Full-Duplex Relaying in MIMO-OFDM Frequency-Selective Channels with Optimal Adaptive Filtering

In-band full-duplex transmission allows a relay station to theoretically double its spectral efficiency by simultaneously receiving and transmitting in the same frequency band, when compared to the traditional half-duplex or out-of-band full-duplex counterpart. Consequently, the induced self-interference suffered by the relay may reach considerable power levels, which decreases the signal-to-interference-plus-noise ratio (SINR) in a decode-and-forward (DF) relay, leading to a degradation of the relay performance. This paper presents a technique to cope with the problem of self-interference in broadband multiple-input multiple-output (MIMO) relays. The proposed method uses a time-domain cancellation in a DF relay, where a replica of the interfering signal is created with the help of a recursive least squares (RLS) algorithm that estimates the interference frequency-selective channel. Its convergence mean time is shown to be negligible by simulation results, when compared to the length of a typical orthogonal-frequency division multiplexing (OFDM) sequences. Moreover, the bit-error-rate (BER) and the SINR in a OFDM transmission are evaluated, confirming that the proposed method extends significantly the range of self-interference power to which the relay is resilient to, when compared with other mitigation schemes

Massive MIMO Full-Duplex Relaying with Optimal Power Allocation for Independent Multipairs

With the help of an in-band full-duplex relay station, it is possible to simultaneously transmit and receive signals from multiple users. The performance of such system can be greatly increased when the relay station is equipped with a large number of antennas on both transmitter and receiver sides. In this paper, we exploit the use of massive arrays to effectively suppress the loopback interference (LI) of a decode-and-forward relay (DF) and evaluate the performance of the end-to-end (e2e) transmission. This paper assumes imperfect channel state information is available at the relay and designs a minimum mean-square error (MMSE) filter to mitigate the interference. Subsequently, we adopt zero-forcing (ZF) filters for both detection and beamforming. The performance of such system is evaluated in terms of bit error rate (BER) at both relay and destinations, and an optimal choice for the transmission power at the relay is shown. We then propose a complexity efficient optimal power allocation (OPA) algorithm that, using the channel statistics, computes the minimum power that satisfies the rate constraints of each pair. The results obtained via simulation show that when both MMSE filtering and OPA method are used, better values for the energy efficiency are attained.Comment: Accepted to the 16th IEEE International Workshop on Signal Processing Advances in Wireless Communications - SPAWC, Stockholm, Sweden 201

Complete design and optimization of multicomponent separation processes: the case study of the quaternary separation of nadolol stereoisomers

The direct chromatographic resolution of enantiomers using chiral stationary phases (CSPs) is actually a very well established separation technique. Several reasons were responsible for the growing success of this technique. The continuous technical development of new chiral stationary phases (CSPs) combined with their commercial availability has been, probably, the most relevant leverage issue. Chiral liquid chromatography is based on different mutual interactions between the molecules that elute with the liquid (solvent and solutes) and the molecules that are present in the stationary phase. Therefore, optimization of a chiral separation is based on the selection of a proper combination between a CSP and a mobile phase (solvent) composition by promoting, in a favourable way, all possible mutual interactions. The optimization will be a much more challenging task if we are leading not with a traditional binary racemic mixture separation problem but if we are interested in the separation of a quaternary chiral mixture. The complexity degree will be significantly increased if we consider a preparative separation, using a technique such as the simulated moving bed technology, were high feed concentrations are normally used in order to improve the process performance. In these situations, the wanted high concentrations of the different chiral solutes inside the chromatographic columns will enhance significantly the mutual competition between solutes for adsorption with the stationary phase. From a preparative point of view, and when considering the choice of the mobile phase (“solvent”) composition, a high selectivity of the enantiomers should not be the only goal to be aimed, as it is frequently the case at analytical scale. Besides the choice of a CSP with high loading capacity, a high solubility of the solutes in the solvent and low retention times should also be taken into account, in order to improve the preparative process performance, as it was extensively explained for the separation of chiral non-steroidal anti-inflammatory drugs1-4 . Nadolol (1-(tert-butyamino)-3-[(5,6,7,8-tetrahydro-cis-6,7-dihydroxy-1-naphthyl)oxy]-2-propanol) is a non-selective beta-adrenergic antagonist pharmaceutical drug. This class of pharmaceutical drugs is prescribed, mainly, to treat arrhythmias, angina pectoris, hypertension, migraine disorders and for tremor. Today, and in spite of the more and more restricted international legislation towards the commercialization of pharmaceutical drugs based on active principles that are made of single enantiomers, nadolol is still only commercially available as an equal mixture of four stereoisomers. This is even more serious due to the considerable evidence, recently made both by the academic community and pharmaceutical industry, that it is important to characterize the single stereochemical components when describing the pharmacodynamics and pharmacokinetics of a racemic drug. The separation of nadolol stereoisomers on CHIRALPAK® AD at both analytical and preparative scales was recently reportedby Ribeiro et al5. However, nowadays no further work was developed to better understand and exploit the capabilities of Chiralpak® IA both for the analytical and preparative chiral separations of nadolol stereoisomers. This work will present a complete methodology concerning experimental, modelling and simulation results. Both the CHIRALPAK® AD and CHIRALPAK® IA CSP will be evaluated. The selection of the proper CSP/solvent combination for preparative operation will be fully study taking into account the screening strategy proposed by Zhang et al6. Additional results include the measurement of nadolol stereoisomers solubilities, equilibrium adsorption data and fixed bed (breakthroughs) experiments. The complete screening of CSP/solvent combination will lead to the choice of the better solutions for the separation of nadolol stereoisomers, considering the target component or components to be obtained. Simulation and experimental results will be presented for the multicomponent separation of nadolol stereoisomers by Simulated Moving Bed adsorption process

Multicomponent chiral separations by analytical and preparative liquid chromatography

This work will present a complete methodology concerning experimental, modelling and simulation results. Both the CHIRALPAK AD and CHIRALPAK IA CSP will be evaluated. The selection of the proper CSP/solvent combination for preparative operation will be fully study taking into account the screening strategy proposed by Zhang et al. Additional results include the measurement of nadolol stereoisomers solubilities, equilibrium adsorption data and fixed bed (breakthroughs) experiments. The complete screening of CSP/solvent combination will lead to the choice of the better solutions for the separation of nadolol stereoisomers, considering the target component or components to be obtained. Simulation and experimental results will be presented for the multicomponent separation of nadolol stereoisomers by multicolumn and Simulated Moving Bed adsorption processes

Influence of mobile phase composition on the preparative separation of profens by chiral liquid chromatography

Liquid chiral chromatography of ketoprofen and flurbiprofen enantiomers is carried out using an amylose-based stationary phase. The mobile phases used for profens chiral separations are usually a hydrocarbon-alcohol combination, with high hydrocarbon content. However, profens show poor solubilities in hydrocarbon solvents when compared to alcohols. When the final objective is high productivity preparative separations, besides retention time, selectivity and column efficiency, solubility of the racemic drug is always a mandatory aspect to take into account. This work shows that an increase of the alcoholic content in the mobile phase is possible without a decrease in selectivity and column efficiency. Considering the chiral separation of ketoprofen and flurbiprofen enantiomers, results show that the mobile phase needs only a small quantity of acidic modifier and can be composed by a high or even pure alcoholic content. Additionally, it is found that the type of alcohol to be used can differ, depending on the profen racemic mixture to be separated

Chiral separation of nadolol stereoisomers by liquid chromatography : screening of mobile phase composition and SMB separation

This work describes a systematic approach to rapid development of simulated moving bed (SMB) chiral chromatographic separations. The presented methodology involves several pulse experiments using a single-column to screen the best mobile phase composition using a Chiralpak AD stationary phase and equilibrium adsorption data used to specify the initial flow rates of the SMB operation

Influence of mobile phase composition on the preparative separation of profens by chiral liquid chromatography

The chirality of drugs is an important issue for the pharmaceutical industry, since the different enantiomers of a racemic drug may have distinct pharmacological activities, pharmacokinetic and pharmacodynamic effects. Because of its chiral selectivity, human body reacts with a racemic drug differently, and metabolise each enantiomer on separate pathways producing different pharmacological activity. Thus, one isomer may produce the desired therapeutic activities, while the other may be inactive or even, in worst cases, produce unwanted effects. Flurbiprofen [2-(2-fluoroo4-biphenyl)-propionic acid] and ketoprofen [2-(3-benzoylphenyl)-propionic acid] belong to a family of chemicals named 2-arylpropionic acids, or profens, an important sub-class of the frequently prescribed and used drugs called nonsteroidal anti-inflammatory drugs (NSAIDs). A considerable number of these drugs possess antipyretic activity in addition to its analgesic and antiinflammatory actions, and thus have utility in the treatment of fever. The main primary indications for NSAIDs therapy include rheumatoid arthritis, osteoarthritis, acute gouty arthritis, ankylosing spondylitis and dysmenorrhea (DeRuiter, 2002). The importance of this class of drugs is supported by U,e fact that, in the last twenty years, drugs like aspirin, phenazone derivatives or acetaminophen are being supplemented by profens (Brune and Hinz, 1998)

Model combination in neural-based forecasting

This paper discusses different ways of combining neural predictive models or neural-based forecasts. The proposed approaches consider Gaussian radial basis function networks, which can be efficiently identified and estimated through recursive/adaptive methods. The usual framework for linearly combining estimates from different models is extended, to cope with the case where the forecasting errors from those models are correlated. A prefiltering methodology is pro posed, addressing the problems raised by heavily nonstationary time series. Moreover, the paper discusses two approaches for decision-making from forecasting models: either inferring decisions from combined predictive estimates, or combining prescriptive solutions derived from different forecasting models.info:eu-repo/semantics/publishedVersio

Revisiting context-aware component interconnection

Software connectors are external coordination devices which ensure the flow of data and enforce synchronization constraints within a component’s network. The specification of software connectors through which context dependent behaviour is correctly propagated remains an open, non trivial issue in their semantics. This paper, building on previous work by the authors, revisits this problem and introduces a model in which context awareness is suitably handled

Preparative separation of profen enantiomers by liquid chromatography

Profens. or 2•aryfpropionic acids. are an important sub-class of the frequently prescribed non-steraidal anti-inflammatory drugs (NSAIDs). Some of the main primary indications for NSAIDs therapy include rheumatoid arthritis, osteoarthritis, acute gouty arthritis, dysmenorrhea and acute pain. Ketoprofen (R.S)-2-(3-benzoylphenylpropionic acid) and Flurbiprofen (R,S)-2-(2-fluoro-4- -biphenylprapionic acid) are examples of NSAIDs, both marketed as racemic mixtures