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Fading statistics in communications - a random matrix approach. Acta Physica Polonica A 120, A–85
No full textFading is the time-dependent variations in signal strength measured at a receiver, due to temporally evolving multipath scattering and interference. In our previous work we introduced a statistical fading model for the time-reversal invariant case by combining the predictions of random matrix theory with the random coupling model that includes system-specific properties such as the radiation impedance of the ports and short-orbit effects. In the high-loss limit this random matrix theory model reduced to the most common fading models in the wireless communication field. In this paper we discuss the theoretical model in more detail and extend it to the case of broken time-reversal invariance
BER Analysis of Various STBC Coding for MIMO Systems at Different Modulation Schemes
Get PDFAbstract: This Paper shows the performance analysis of Bit Error Rate (BER) in MIMO system using STBC codes. We compare OSTBC scheme with different coding schemes viz; ABBA, Jafarkhani and Tarkoh at different modulation methods viz ; PSK, QAM. Zero-Forcing (ZF) , Minimum Mean Square Error (MMSE) equalization techniques are used for achieve full diversity. Keywords: BER, MIMO, STBCs, ZF, MMSE I . INTRODUCTION An Improving demand for services for the wireless systems has turned wide variety into a valuable resource. MultipleInput-Multiple-Output (MIMO) wireless channels have considerably higher capacities than traditional channels. Fading makes it extremely difficult for the receiver to recover the transmitted signal unless the receiver is provided with some form of diversity i.e. replicas of same transmitted signal with uncorrelated attenuation. In fact, diversity combining technology has been one of the most important contributors to reliable wireless communications. Consider transmit diversity by deploying multiple antennas at the base station. Moreover, in economic terms, the cost of multiple antennas at the base station can be amortized over numerous mobile users. Hence transmit diversity has been identified as one of the key contributing technologies to the downlinks of 3G wireless such as W-CDMA and CDMA2000. There are generally three categories of transmit diversity. Feedback Scheme: This involves the feedback of channel state information (CSI, typically including channel gain phase information) from the receiver to transmitter in order to adapt the transmitter to the channel during the next transmission epochs. It is also commonly known as the "closed-loop" system. Feedback forward Scheme: This involves the receiver making use of feed forward information sent by transmitter, such as pilot symbols, to estimate the channel, but no channel feedback information is sent back to the transmitter. It is also known as "open-loop" or "coherent" system. Blind Scheme: This requires no feedback of CSI or feed-forward of pilots, and the receiver simply makes use of the received signal to attempt data recovery without knowledge of CSI. It is also known as the "non-coherent" system. Space-Time Coding (STC) is technique that combines coding, modulation and signal processing to achieve diversity. The first STC proposed in the literature is Space-Time Trellis Code (STTC), which has a good decoding performance but decoding complexity that increases exponentially with transmission rate. In addressing the issue of decoding complexity of STTC, Space-Time Block Code (STBC) was subsequently proposed. Alamouti [1] discovered a remarkable STBC scheme for two transmit antennas. This scheme supports linear decoding complexity for Maximumlikehood (ML) decoding, which is much simpler than decoding of STTC. Alamouti's scheme is very appealing in terms of implementation simplicity. Hence it motivates a Search for similar schemes for more than two antennas, to achieve full diversity level higher than two. As a result , Orthogonal Space-Time Block Codes (OSTBC) was introduced by tarko
Influence of metal properties on the effectiveness of zero valent iron nanoparticles for soil remediation
No full textAbstract The advances in nanotechnology have induced an increase in the use of nanomaterials in every sector of society, ranging from enhanced drug delivery to new methods for the treatment of polluted soil and groundwater (nanoremediation). In recent years, the environmental application of nanoscale zero-valent iron (nZVI) has generated a great deal of attention due to its potential for cost reduction compared to other in situ treatments, higher reactivity and broader applications. Several recent studies provided valuable insights into key nZVI properties associated with the potential to transform chlorinated organic compounds, metal ions such as Cd, Ni, Zn, As, Cr, Ag, and Pb, as well as notorious inorganic anions like perchlorate and nitrat
Effects of low-dose intranasal (S)-ketamine in patients with neuropathic pain
No full texta b s t r a c t Background: NMDA receptors are involved in the development and maintenance of neuropathic pain. We evaluated the efficacy and safety of intranasal (S)-ketamine, one of the most potent clinically available NMDA receptor antagonists. Methods: Sixteen patients with neuropathic pain of various origins were randomized into two treatment groups: (S)-ketamine 0.2 mg/kg (group 1); (S)-ketamine 0.4 mg/kg (group 2). Plasma concentrations of (S)-ketamine and (S)-norketamine were measured over 6 h by High Performance Liquid Chromatography combined with mass spectrometry. Quantitative sensory testing (QST) was conducted before, during and after treatment. Side effects and amount of pain reduction were recorded. Results: Intranasal (S)-ketamine administration lead to peak plasma concentrations of 27.7 ± 5.9 ng/ml at 10 ± 6.3 min (group 1) and 34.3 ± 22.2 ng/ml at 13.8 ± 4.8 min after application (group 2). Maximal plasma concentrations of (S)-norketamine were 18.3 ± 14.9 ng/ml at 81 ± 59 min (group 1) and 34.3 ± 5.5 ng/ml at 75 ± 40 min (group 2). Pain scores decreased significantly in both groups with minimal pain at 60 min after drug administration (70 ± 10% and 61 ± 13% of initial pain in groups 1 and 2). The time course of pain decrease was significantly correlated with plasma concentrations of (S)-ketamine and (S)-norketamine (partial correlations: (S)-norketamine: À0.90 and À0.86; (S)-ketamine: À0.72 and À0.71 for group 1 and group 2, respectively). Higher dosing elicited significantly more side effects. Intranasal (S)-ketamine had no significant impact on thermal or mechanical detection and pain thresholds in normal or symptomatic skin areas. Conclusions: Intranasal administration of low dose (S)-ketamine rapidly induces adequate plasma concentrations of (S)-ketamine and subsequently of its metabolite (S)-norketamine. The time course of analgesia correlated with plasma concentrations
Importers, Exporters and the Division of the Gains from Trade *
No full textAbstract This paper examines the microstructure of import markets and the division of the gains from trade among consumers, importers and exporters. When exporters and importers transact through anonymous markets, double marginalization and business stealing among competing importers lead to lower profits. Trading parties can overcome these inefficiencies by investing in richer arrangements to ensure bilateral profit maximization that eliminates double marginalization and joint profit maximization that also internalizes business stealing. The introduction of endogenous microstructure of import markets in a trade model means that trade liberalization can increase the incentive to engage in joint profit maximization, thus raising the profits of exporters and importers at the expense of consumer welfare. Following the US-Colombia free trade agreement, US exporters that received tariff reductions were more likely to increase their average price, decrease their quantity exported and reduce the number of import partners. As predicted by the theory, this import market consolidation occurs for medium-sized US exporters, who increase their average tariff-inclusive price by as much as 6 per cent, leading to a shift in surplus from the liberalizing country to the exporting country
Genetic differentiation within and between four UK ethnic groups
No full textAbstract In previous papers [L.A. Foreman, J.A. Lambert, I.W. Evett, Regional genetic variation in Caucasians, Forensic Sci. Int. 95 (1998) 27±37; L.A. Foreman, Analyses to investigate appropriate measures of differentiation between European Caucasian populations using short tandem repeat (STR) data, FSS Research Report FSS-RR-804 (1999)], we have carried out detailed investigations of the level of regional and national variation in STR characteristics exhibited within white Caucasian populations. The studies described here extend our earlier work to the black African/Caribbean and Asian (Indo-Pakistani) populations of the UK, routinely considered in casework calculations at the Forensic Science Service (FSS). In addition, estimation of allele distributions and database comparisons are carried out for two further populations, i.e. those classi®ed as containing individuals of Oriental and Arabic appearance.
PIXEL CLASSIFICATION OF SATELLITE IMAGES USING A NOVEL PAIR WISE KERNEL FUNCTION SVM
No full textABSTRACT In this paper we have proposed a symmetric, positive semi definite kernel function for support vector machine classifier. Pixel classification is a form of supervised image segmentation where the actual object classes present in the image are known a priori. In case of satellite image, this prior information plays a huge role to estimate the actual statistics of different land covers. The state of the art kernels have the problem to clearly separate closely spaced data points, as in the case of image pixels of satellite images, where there are no sharp changes between two different regions in terms of the pixel intensity. The proposed kernel has overcome this difficulty with the previous kernels effectively and has good generalization capability. Experimental results establishes the fact when the proposed kernel based SVM has been used for supervised satellite image segmentation purpose