Joint Scheduling and Resource Allocation in the OFDMA Downlink: Utility Maximization under Imperfect Channel-State Information

We consider the problem of simultaneous user-scheduling, power-allocation, and rate-selection in an OFDMA downlink, with the goal of maximizing expected sum-utility under a sum-power constraint. In doing so, we consider a family of generic goodput-based utilities that facilitate, e.g., throughput-based pricing, quality-of-service enforcement, and/or the treatment of practical modulation-and-coding schemes (MCS). Since perfect knowledge of channel state information (CSI) may be difficult to maintain at the base-station, especially when the number of users and/or subchannels is large, we consider scheduling and resource allocation under imperfect CSI, where the channel state is described by a generic probability distribution. First, we consider the "continuous" case where multiple users and/or code rates can time-share a single OFDMA subchannel and time slot. This yields a non-convex optimization problem that we convert into a convex optimization problem and solve exactly using a dual optimization approach. Second, we consider the "discrete" case where only a single user and code rate is allowed per OFDMA subchannel per time slot. For the mixed-integer optimization problem that arises, we discuss the connections it has with the continuous case and show that it can solved exactly in some situations. For the other situations, we present a bound on the optimality gap. For both cases, we provide algorithmic implementations of the obtained solution. Finally, we study, numerically, the performance of the proposed algorithms under various degrees of CSI uncertainty, utilities, and OFDMA system configurations. In addition, we demonstrate advantages relative to existing state-of-the-art algorithms

Evolution of green shipping research: themes and methods

Over the past 30 years, there have been growing concerns on theenvironmental impacts of maritime transportation, which have attractedgreat attention from both academia and practitioners. Understandingdevelopments in this area can help guide future research. We conducteda comprehensive review of green shipping research, comprising 213papers published in transportation journals in SSCI of 2017 over theperiod 1988–2017. We find that research on green shipping hasincreased greatly since 2012, accounting for 77.5% of the reviewedpapers. The main focus today on green shipping was on air pollution,and the classification of green shipping practice, such as technical measures,operational options, market-based measures, and recycling andreusing, is becoming clear. According to the existing studies, futureresearch on green shipping must strengthen technology research tonot only solve practical problems, but also to establish a theoreticalgreen shipping system. Moreover, researchers from different countriescould cooperate with each other to give effective suggestions on settingstandards and laws of green shipping. Finally, we identify the futureresearch themes will focus on setting up green shipping system andlegislation and policy

Spectrum sharing models in cognitive radio networks

Spectrum scarcity demands thinking new ways to manage the distribution of radio frequency bands so that its use is more effective. The emerging technology that can enable this paradigm shift is the cognitive radio. Different models for organizing and managing cognitive radios have emerged, all with specific strategic purposes. In this article we review the allocation spectrum patterns of cognitive radio networks and analyse which are the common basis of each model.We expose the vulnerabilities and open challenges that still threaten the adoption and exploitation of cognitive radios for open civil networks.L'escassetat de demandes d'espectre fan pensar en noves formes de gestionar la distribució de les bandes de freqüència de ràdio perquè el seu ús sigui més efectiu. La tecnologia emergent que pot permetre aquest canvi de paradigma és la ràdio cognitiva. Han sorgit diferents models d'organització i gestió de les ràdios cognitives, tots amb determinats fins estratègics. En aquest article es revisen els patrons d'assignació de l'espectre de les xarxes de ràdio cognitiva i s'analitzen quals són la base comuna de cada model. S'exposen les vulnerabilitats i els desafiaments oberts que segueixen amenaçant l'adopció i l'explotació de les ràdios cognitives per obrir les xarxes civils.La escasez de demandas de espectro hacen pensar en nuevas formas de gestionar la distribución de las bandas de frecuencia de radio para que su uso sea más efectivo. La tecnología emergente que puede permitir este cambio de paradigma es la radio cognitiva. Han surgido diferentes modelos de organización y gestión de las radios cognitivas, todos con determinados fines estratégicos. En este artículo se revisan los patrones de asignación del espectro de las redes de radio cognitiva y se analizan cuales son la base común de cada modelo. Se exponen las vulnerabilidades y los desafíos abiertos que siguen amenazando la adopción y la explotación de las radios cognitivas para abrir las redes civiles

Modeling water resources management at the basin level: review and future directions

Water quality / Water resources development / Agricultural production / River basin development / Mathematical models / Simulation models / Water allocation / Policy / Economic aspects / Hydrology / Reservoir operation / Groundwater management / Drainage / Conjunctive use / Surface water / GIS / Decision support systems / Optimization methods / Water supply

Evaluating CAP alternative policy scenarios through a system dynamics approach in rural areas of Greece

Current considerations for the post-2013 CAP create the need for the investigation and evaluation of alternative CAP scenarios and their effects on agriculture, environment and regional development in EU rural areas. To this end, a system-dynamics model is developed and utilized to evaluate the impacts of alternative CAP scenarios in a Greek rural area (prefecture of Trikala). This particular model features four basic subsystems (agriculture, environment, regional economy and human resources) specified and analyzed through a linear programming model, a dynamic input-output model and an age-cohort demographic model, respectively. Four alternative policy scenarios are specified, dealing with possible developments on Pillars 1 and 2. Model simulations produce scenario-specific effects for the 2007-2013 period, and up to 2020 in the form of changes in land use and farm output, environmental indicators associated with farm activity, economy-wide impacts and impacts on local population. Results show that different future orientations for the CAP are associated with different impacts on agricultural activity, the environment and total economic activity in this area. A reduction of Pillar 1 funds and a dedication of Pillar 2 spending on Axis 2 generate negative effects on local agriculture, but benefit the local environment and economy-wide incomes. On the other hand, a more “productive” orientation of Pillar 2 positively affects local employment (compared to the current CAP) but does not create any positive or negative effects on the environment of this regionCAP, policy impact assessment, rural development, system dynamics, Agricultural and Food Policy, C61, C67, Q18, R58,

Applications of negotiation theory to water issues

The authors review the applications of noncooperative bargaining theory to waterrelated issues-which fall in the category of formal models of negotiation. They aim to identify the conditions under which agreements are likely to emerge and their characteristics, to support policymakers in devising the"rules of the game"that could help obtain a desired result. Despite the fact that allocation of natural resources, especially trans-boundary allocation, has all the characteristics of a negotiation problem, there are not many applications of formal negotiation theory to the issue. Therefore, the authors first discuss the noncooperative bargaining models applied to water allocation problems found in the literature. Key findings include the important role noncooperative negotiations can play in cases where binding agreements cannot be signed; the value added of politically and socially acceptable compromises; and the need for a negotiated model that considers incomplete information over the negotiated resource.Water Supply and Sanitation Governance and Institutions,Town Water Supply and Sanitation,Water and Industry,Environmental Economics&Policies,Water Conservation

Groundwater research and management: integrating science into management decisions. Proceedings of IWMI-ITP-NIH International Workshop on "Creating Synergy Between Groundwater Research and Management in South and Southeast Asia," Roorkee, India, 8-9 February 2005

Groundwater management / Governance / Groundwater development / Artificial recharge / Water quality / Aquifers / Groundwater irrigation / Water balance / Simulation models / Watershed management / Water harvesting / Decision making / South East Asia / Bangladesh / China / India / Nepal / Pakistan / Syria

Economics of irrigation water management : a literature survey with focus on partial and general equilibrium models

Water policy is an important topic on the agenda of the international community, and efficiency and equity in the allocation of water have emerged as important factors to be considered. Water pricing can be used to mitigate both the quantity and quality dimensions of water scarcity. This paper reviews partial equilibrium models and general equilibrium models that are relevant to irrigation water management issues. The most widely discussed issues in these models are water markets and water pricing. The interrelationships between economic, cultural, social, and political aspects that are related to water policy make it difficult to provide a comprehensive policy analysis. General equilibrium models of irrigation water management allow incorporation of both the irrigation sector and the other sectors in the economy and analysis of policies affecting each of them and the interaction between them. In addition to being able to address sector and household specifications, production factors, time horizon, pricing policies, and institutions such as water markets, general equilibrium models allow the analysis of the impact of water policies on equity and poverty alleviation. The authors conclude that, although there has been a significant increase in efforts to analyzewater related problems, analytical and empirical research in the field is still deficient and more effort is needed to address them.Environmental Economics&Policies,Water Supply and Sanitation Governance and Institutions,Town Water Supply and Sanitation,Water Supply and Systems,Water Conservation