Multiuser Scheduling for Cognitive MIMO with Channel Estimation Errors and Feedback Delay

A multiuser scheduling multiple-input multiple-output (MIMO) cognitive radio network (CRN) with space-time block coding (STBC) is considered in this paper, where one secondary base station (BS) communicates with one secondary user (SU) selected from K candidates. The joint impact of imperfect channel state information (CSI) in BS → SUs and BS → PU due to channel estimation errors and feedback delay on the outage performance is firstly investigated. We obtain the exact outage probability expressions for the considered network under the peak interference power IP at PU and maximum transmit power Pm at BS which cover perfect/imperfect CSI scenarios in BS → SUs and BS → PU. In addition, asymptotic expressions of outage probability in high SNR region are also derived from which we obtain several important insights into the system design. For example, only with perfect CSIs in BS → SUs, i.e., without channel estimation errors and feedback delay, the multiuser diversity can be exploited. Finally, simulation results confirm the correctness of our analysis.

Prevalence, Nature, Severity and Risk Factors for Prescribing Errors in Hospital Inpatients: Prospective Study in 20 UK Hospitals

Introduction: It has been suggested that doctors in their first year of post-graduate training make a disproportionate number of prescribing errors.

Obkective: This study aimed to compare the prevalence of prescribing errors made by first-year post-graduate doctors with that of errors by senior doctors and non-medical prescribers and to investigate the predictors of potentially serious prescribing errors.

Methods: Pharmacists in 20 hospitals over 7 prospectively selected days collected data on the number of medication orders checked, the grade of prescriber and details of any prescribing errors. Logistic regression models (adjusted for clustering by hospital) identified factors predicting the likelihood of prescribing erroneously and the severity of prescribing errors.

Results: Pharmacists reviewed 26,019 patients and 124,260 medication orders; 11,235 prescribing errors were detected in 10,986 orders. The mean error rate was 8.8 % (95 % confidence interval [CI] 8.6-9.1) errors per 100 medication orders. Rates of errors for all doctors in training were significantly higher than rates for medical consultants. Doctors who were 1 year (odds ratio [OR] 2.13; 95 % CI 1.80-2.52) or 2 years in training (OR 2.23; 95 % CI 1.89-2.65) were more than twice as likely to prescribe erroneously. Prescribing errors were 70 % (OR 1.70; 95 % CI 1.61-1.80) more likely to occur at the time of hospital admission than when medication orders were issued during the hospital stay. No significant differences in severity of error were observed between grades of prescriber. Potentially serious errors were more likely to be associated with prescriptions for parenteral administration, especially for cardiovascular or endocrine disorders.

Conclusions: The problem of prescribing errors in hospitals is substantial and not solely a problem of the most junior medical prescribers, particularly for those errors most likely to cause significant patient harm. Interventions are needed to target these high-risk errors by all grades of staff and hence improve patient safety.

Preparing assessments and examinations. Common errors and good practice.

Assessment forms an important part of the student learning experience and students place a high value on the quality of feedback that they receive from academic staff on where they might improve on their examinations or assignments. However while feedback is important the quality of the actual assessment itself before students undertake an examination or commence writing an assignment is also important. It is imperative that students are clear in their understanding of what is expected of them in order to achieve a particular grade and that there is lack of ambiguity in examinations or assignments. Biggs (2003) highlighted the importance of clarity in what students are expected to be able to do at the end of a unit of study, and that intended learning outcomes should be clearly aligned to the assessment and communicated to students so that they can structure their learning activities to optimize their assessment performance. However as Rust (2002) highlighted there are often inconsistencies in assessment practices ranging from a mis-match of assessment and learning outcomes to the inclusion of additional learning criteria and lack of clarity in the instructions. Such inconsistencies and unacceptable errors in examination papers can undermine student confidence in the assessment process
In order to try and minimise such inconsistencies an internal assessment group was set up October 2013 within the School of Nursing and Midwifery at Queens University Belfast, consisting of representative academic staff from across the range of undergraduate and post graduate courses in nursing and midwifery. The assessment group was to be a point of reference for all school examinations with a particular remit to develop an assessment strategy for all nursing and midwifery programmes and to ensure that all assessments comply with current best practice and with Nursing and Midwifery Council (NMC) requirements.
Aim
This paper aims to highlight some examples of good practice and common errors that were found in assignments and examinations that were submitted to the assessment group for review.
References

Biggs. J. (2003) Teaching for Quality Learning at University – What the Student Does 2nd Edition SRHE / Open University Press, Buckingham.
Rust, C.( 2002) The impact of assessment on student learning, Active Learning in Higher education Vol3(2):145-158

The prevalence of refractive errors among adults in the United States, Western Europe, and Australia.

OBJECTIVE:

To estimate the prevalence of refractive errors in persons 40 years and older.

METHODS:

Counts of persons with phakic eyes with and without spherical equivalent refractive error in the worse eye of +3 diopters (D) or greater, -1 D or less, and -5 D or less were obtained from population-based eye surveys in strata of gender, race/ethnicity, and 5-year age intervals. Pooled age-, gender-, and race/ethnicity-specific rates for each refractive error were applied to the corresponding stratum-specific US, Western European, and Australian populations (years 2000 and projected 2020).

RESULTS:

Six studies provided data from 29 281 persons. In the US, Western European, and Australian year 2000 populations 40 years or older, the estimated crude prevalence for hyperopia of +3 D or greater was 9.9%, 11.6%, and 5.8%, respectively (11.8 million, 21.6 million, and 0.47 million persons). For myopia of -1 D or less, the estimated crude prevalence was 25.4%, 26.6%, and 16.4% (30.4 million, 49.6 million, and 1.3 million persons), respectively, of whom 4.5%, 4.6%, and 2.8% (5.3 million, 8.5 million, and 0.23 million persons), respectively, had myopia of -5 D or less. Projected prevalence rates in 2020 were similar.

CONCLUSIONS:

Refractive errors affect approximately one third of persons 40 years or older in the United States and Western Europe, and one fifth of Australians in this age group.

Joint compensation of IQ-imbalance and carrier phase sychronization errors in communication receivers

This work addresses the joint compensation of IQimbalances and carrier phase synchronization errors of zero- IF receivers. The compensation scheme based on blind-source separation which provides simple yet potent means to jointly compensate for these errors independent of modulation format and constellation size used. The low-complexity of the algorithm makes it a suitable option for real-time deployment as well as practical for integration into monolithic receiver designs.

Performance of an adaptive homodyne receiver in the presence of multipath, Rayleigh-fading and time-varying quadrature errors

In this paper, we carry out a detailed performance analysis of the blind source separation based I/Q corrector operating at the baseband. Performance of the digital I/Q corrector is evaluated not only under time-varying phase and gain errors but also in the presence of multipath and Rayleigh fading channels. Performance under low-SNR and different modulation formats and constellation sizes is also evaluated. What is more, BER improvement after correction is illustrated. The results indicate that the adaptive algorithm offers adequate performance for most communication applications hence, reducing the matching requirements of the analog front-end enabling higher levels of integration.

Correction of transmitter gain and phase errors at the receiver

This paper explores the benefits of compensating transmitter gain and phase inbalances in the receiver for quadrature communication systems. It is assumed that the gain and phase imbalances are introduced at the transmitter only. A simple non-data aided DSP algorithm is used at the reciever to compensate for the imbalances. Computer simulation has been formed to study a coherent QPSK communication system.