Energy-Efficient Power Allocation in OFDM Systems with Wireless Information and Power Transfer

This paper considers an orthogonal frequency division multiplexing (OFDM) downlink point-to-point system with simultaneous wireless information and power transfer. It is assumed that the receiver is able to harvest energy from noise, interference, and the desired signals. We study the design of power allocation algorithms maximizing the energy efficiency of data transmission (bit/Joule delivered to the receiver). In particular, the algorithm design is formulated as a high-dimensional non-convex optimization problem which takes into account the circuit power consumption, the minimum required data rate, and a constraint on the minimum power delivered to the receiver. Subsequently, by exploiting the properties of nonlinear fractional programming, the considered non-convex optimization problem, whose objective function is in fractional form, is transformed into an equivalent optimization problem having an objective function in subtractive form, which enables the derivation of an efficient iterative power allocation algorithm. In each iteration, the optimal power allocation solution is derived based on dual decomposition and a one-dimensional search. Simulation results illustrate that the proposed iterative power allocation algorithm converges to the optimal solution, and unveil the trade-off between energy efficiency, system capacity, and wireless power transfer: (1) In the low transmit power regime, maximizing the system capacity may maximize the energy efficiency. (2) Wireless power transfer can enhance the energy efficiency, especially in the interference limited regime.Comment: 6 pages, Accepted for presentation at the IEEE International Conference on Communications (ICC) 201

Energy-Efficient Resource Allocation in Multiuser OFDM Systems with Wireless Information and Power Transfer

In this paper, we study the resource allocation algorithm design for multiuser orthogonal frequency division multiplexing (OFDM) downlink systems with simultaneous wireless information and power transfer. The algorithm design is formulated as a non-convex optimization problem for maximizing the energy efficiency of data transmission (bit/Joule delivered to the users). In particular, the problem formulation takes into account the minimum required system data rate, heterogeneous minimum required power transfers to the users, and the circuit power consumption. Subsequently, by exploiting the method of time-sharing and the properties of nonlinear fractional programming, the considered non-convex optimization problem is solved using an efficient iterative resource allocation algorithm. For each iteration, the optimal power allocation and user selection solution are derived based on Lagrange dual decomposition. Simulation results illustrate that the proposed iterative resource allocation algorithm achieves the maximum energy efficiency of the system and reveal how energy efficiency, system capacity, and wireless power transfer benefit from the presence of multiple users in the system.Comment: 6 pages. The paper has been accepted for publication at the IEEE Wireless Communications and Networking Conference (WCNC) 2013, Shanghai, China, Apr. 201

Cyclo­pentyl­diphen­yl(4-thio­semi­carbazonopenta­noato-κO)tin(IV)

The Sn atom in the title compound, [Sn(C5H9)(C6H5)2(C6H10N3O2S)], exists within a tetra­hedral geometry. The –NH2 group forms a weak hydrogen bond across a center of inversion to the S atom of an adjacent mol­ecule, as well as another weaker hydrogen (across another center of inversion) to the Sn-bound O atom of another mol­ecule. The hydrogen-bonded layer structure is consolidated by a strong hydrogen bond between the –NH– group and the uncoordinated O atom of a third mol­ecule

Molecular diagnosis of severe acute respiratory syndrome.

The etiologic agent of severe acute respiratory syndrome (SARS) has been identified as a new type of coronavirus, known as SARS-coronavirus (SARS-CoV). Although the SARS epidemic has subsided, many authorities, including the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), have warned of the possible re-emergence of this highly infectious disease. Although antibody-based diagnosis of SARS has been demonstrated to be a reliable proof of SARS infection, it is not sensitive enough for detection during the early phase of the disease. To date, based on the publicly released full genomic sequences of SARS-CoV, various molecular detection methods based on reverse-transcription polymerase chain reaction (RT-PCR) have been developed. Although most of the assays have initially been focused on RNA extracted from nasopharyngeal aspirates, urine, and stools, several of the more recently developed assays have been based on the analysis of RNA extracted from plasma and serum. Such assays allow the more standardized quantitative expression of viral loads and are potentially useful for early SARS diagnosis. In this chapter, two real-time quantitative RT-PCR systems for the quantification of SARS-CoV RNA in serum are discussed. The two RT-PCR systems, one aimed toward the nucleocapsid region and the other toward the polymerase region of the virus genome, have a detection rate of up to 80% during the first week of illness. These quantitative systems are potentially useful for the early diagnosis of SARS and can also provide viral load information that might assist clinicians in making a prognostic evaluation of an infected individual.postprin

Hepatic progenitor cells: their role and functional significance in the new classification of primary liver cancers

Hepatic progenitor cells (HPCs) are bipotential cells residing in normal liver. Their proliferation is observed in reactive conditions of the liver and in primary liver cancers. The observation that some hepatocellular carcinomas (HCCs) express a biliary-like immunophenotype has led to the identification of HPCs in HCC. Accumulating evidence suggests that HPCs play a role as the cell of origin in a variety of primary liver cancers. This has led to the development of revolutionary concepts in hepatocarcinogenesis. In this article, the role and significance of HPCs in HCC, including its classification, are summarized and discussed.postprin

Dipyridinium tribromidochloridobis(4-chloro­phen­yl)stannate(IV)

The tin atom in the substituted ammonium stannate(IV), (C5H6N)2[SnBr3(C6H4Cl)2Cl], lies on a center of symmetry in a distorted octa­hedral coordination geometry. Each independent halogen site is occupied by bromine and chlorine anions in an approximate 3:1 ratio. The pyridinium cation forms a hydrogen bond to only one of the halogen atoms

Bis[4-(dimethyl­amino)pyridinium] tetra­bromidocobaltate(II)

The metal atom in the title salt, (C7H11N2)2[CoBr4], shows a slightly distorted tetra­hedral coordination. The cation forms an N—H⋯Br hydrogen bond to one of the two Br atoms. The CoII atom lies on a special position of 2 site symmetry