Adaptive access and rate control of CSMA for energy, rate and delay optimization

In this article, we present a cross-layer adaptive algorithm that dynamically maximizes the average utility function. A per stage utility function is defined for each link of a carrier sense multiple access-based wireless network as a weighted concave function of energy consumption, smoothed rate, and smoothed queue size. Hence, by selecting weights we can control the trade-off among them. Using dynamic programming, the utility function is maximized by dynamically adapting channel access, modulation, and coding according to the queue size and quality of the time-varying channel. We show that the optimal transmission policy has a threshold structure versus the channel state where the optimal decision is to transmit when the wireless channel state is better than a threshold. We also provide a queue management scheme where arrival rate is controlled based on the link state. Numerical results show characteristics of the proposed adaptation scheme and highlight the trade-off among energy consumption, smoothed data rate, and link delay.This study was supported in part by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under projects COMONSENS (CSD2008-00010, CONSOLIDER-INGENIO 2010 program) and COSIMA (TEC2010-19545-C04-03), in part by Iran Telecommunication Research Center under contract 6947/500, and in part by Iran National Science Foundation under grant number 87041174. This study was completed while M. Khodaian was at CEIT and TECNUN (University of Navarra)

Optimal Policy of Cross-Layer Design for Channel Access and Transmission Rate Adaptation in Cognitive Radio Networks

In this paper, we investigate the cross-layer design of joint channel access and transmission rate adaptation in CR networks with multiple channels for both centralized and decentralized cases. Our target is to maximize the throughput of CR network under transmission power constraint by taking spectrum sensing errors into account. In centralized case, this problem is formulated as a special constrained Markov decision process (CMDP), which can be solved by standard linear programming (LP) method. As the complexity of finding the optimal policy by LP increases exponentially with the size of action space and state space, we further apply action set reduction and state aggregation to reduce the complexity without loss of optimality. Meanwhile, for the convenience of implementation, we also consider the pure policy design and analyze the corresponding characteristics. In decentralized case, where only local information is available and there is no coordination among the CR users, we prove the existence of the constrained Nash equilibrium and obtain the optimal decentralized policy. Finally, in the case that the traffic load parameters of the licensed users are unknown for the CR users, we propose two methods to estimate the parameters for two different cases. Numerical results validate the theoretic analysis

Guide on Diabetes and COVID-19 for Healthcare Professionals in Bangladesh

The world is suffering from a pandemic of coronavirus disease-2019 (COVID-19), and people with diabetes mellitus (DM) are more vulnerable to the serious effects of the COVID-19. This interaction is alarming, considering the high transmission rate of COVID-19 and the global prevalence of DM. Considering the importance of the link between COVID-19 and DM, Bangladesh Diabetic Association has formed a panel of national and international experts in the field of public health, diabetes, and endocrinology to provide some evidence-based guidance for the prevention and care of people with DM during the COVID-19 pandemic

Guide on Diabetes and COVID-19 for Healthcare Professionals in Bangladesh

The world is suffering from a pandemic of coronavirus disease-2019 (COVID-19), and people with diabetes mellitus (DM) are more vulnerable to the serious effects of the COVID-19. This interaction is alarming, considering the high transmission rate of COVID-19 and the global prevalence of DM. Considering the importance of the link between COVID-19 and DM, Bangladesh Diabetic Association has formed a panel of national and international experts in the field of public health, diabetes, and endocrinology to provide some evidence-based guidance for the prevention and care of people with DM during the COVID-19 pandemic