Training Optimization for Gauss-Markov Rayleigh Fading Channels

In this paper, pilot-assisted transmission over Gauss-Markov Rayleigh fading channels is considered. A simple scenario, where a single pilot signal is transmitted every T symbols and T-1 data symbols are transmitted in between the pilots, is studied. First, it is assumed that binary phase-shift keying (BPSK) modulation is employed at the transmitter. With this assumption, the training period, and data and training power allocation are jointly optimized by maximizing an achievable rate expression. Achievable rates and energy-per-bit requirements are computed using the optimal training parameters. Secondly, a capacity lower bound is obtained by considering the error in the estimate as another source of additive Gaussian noise, and the training parameters are optimized by maximizing this lower bound.Comment: To appear in the Proc. of the 2007 IEEE International Conference on Communication

THINGS WERE BETTER IN COMMUNISM; DISSATISFACTION IN KYRGYZSTAN IN THE POST-COMMUNIST PERIOD

This study reflects the survey’s results conducted among Kyrgyz people on their assessment on their satisfaction levels during capitalism and communism. Survey’s results indicate that people have a great dissatisfaction due to harsh economic conditions, insecure labor market, poor education quality, and political instability during transition to capitalism. Moreover, they lost their hope for the future. Especially, age is a determinant factor for the reaction (angriness) against the current economic system

A Macro Economic Analysis of Child Labour in Sub-Saharan Countries

The aims of the research are to assess child labor at the macro level-focusing on education- and to formulize national policies to address this problem in sub-Saharan Africa. We will investigate if some policies such as compulsory education, export banned, credit market, reduction of poverty and increase welfare programs, mechanization of land, population growth and foreign aid are effective to reduce child labor. Key Words: Child Labor, Macro Economy, Sub Saharan Afric

Cognitive radio transmission under QoS constraints and interference limitations

In this article, the performance of cognitive transmission under quality of service (QoS) constraints and interference limitations is studied. Cognitive secondary users are assumed to initially perform sensing over multiple frequency bands (or equivalently channels) to detect the activities of primary users. Subsequently, they perform transmission in a single channel at variable power and rates depending on the channel sensing decisions and the fading environment. A state transition model is constructed to model this cognitive operation. Statistical limitations on the buffer lengths are imposed to take into account the QoS constraints of the cognitive secondary users. Under such QoS constraints and limitations on the interference caused to the primary users, the maximum throughput is identified by finding the effective capacity of the cognitive radio channel. Optimal power allocation strategies are obtained and the optimal channel selection criterion is identified. The intricate interplay between effective capacity, interference and QoS constraints, channel sensing parameters and reliability, fading, and the number of available frequency bands is investigated through numerical results.National Science Foundation/CNS-0834753National Science Foundation/CCF-091726

Performance Analysis of Cognitive Radio Systems under QoS Constraints and Channel Uncertainty

In this paper, performance of cognitive transmission over time-selective flat fading channels is studied under quality of service (QoS) constraints and channel uncertainty. Cognitive secondary users (SUs) are assumed to initially perform channel sensing to detect the activities of the primary users, and then attempt to estimate the channel fading coefficients through training. Energy detection is employed for channel sensing, and different minimum mean-square-error (MMSE) estimation methods are considered for channel estimation. In both channel sensing and estimation, erroneous decisions can be made, and hence, channel uncertainty is not completely eliminated. In this setting, performance is studied and interactions between channel sensing and estimation are investigated. Following the channel sensing and estimation tasks, SUs engage in data transmission. Transmitter, being unaware of the channel fading coefficients, is assumed to send the data at fixed power and rate levels that depend on the channel sensing results. Under these assumptions, a state-transition model is constructed by considering the reliability of the transmissions, channel sensing decisions and their correctness, and the evolution of primary user activity which is modeled as a two-state Markov process. In the data transmission phase, an average power constraint on the secondary users is considered to limit the interference to the primary users, and statistical limitations on the buffer lengths are imposed to take into account the QoS constraints of the secondary traffic. The maximum throughput under these statistical QoS constraints is identified by finding the effective capacity of the cognitive radio channel. Numerical results are provided for the power and rate policies

Cardiogenic Shock Due to Coronary Artery Stent Thrombosis

Stent thrombosis is an uncommon but serious complication that causes sudden death or myocardial infarction (MI). A large MI, especially with ST elevation, can cause cardiogenic shock and pose a significant incidence of morbidity and mortality. Largeness of ischemic territory is the main reason that causes cardiogenic shock. The fundamental treatment strategies are immediate coronary revascularization and perfusion support to avoid end organ damage with medically or mechanical in intensive care units. The prevention, incidences, mechanisms, management, and clinical impacts of cardiogenic shock discussed under this topic