High-rate punctured convolutional self-doubly orthogonal codes for iterative threshold decoding

The puncturing technique allows obtaining high-rate convolutional codes from low-rate convolutional codes used as mother codes. This technique has been successfully applied to generate good high-rate convolutional codes which are suitable for Viterbi and sequential decoding. In this paper, we investigate the puncturing technique for convolutional self-doubly orthogonal codes (CSO/sup 2/C) which are decoded using an iterative threshold-decoding algorithm. Based on an analysis of iterative threshold decoding of the rate-R=b/(b+1) punctured systematic CSO/sup 2/C, the required properties of the rate-R=1/2 systematic convolutional codes (SCCs) used as mother codes are derived. From this analysis, it is shown that there is no need for the punctured mother codes to respect all the required conditions, in order to maintain the double orthogonality at the second iteration step of the iterative threshold-decoding algorithm. The results of the search for the appropriate rate-R=1/2 SCCs used as mother codes to yield a large number of punctured codes of rates 2/3/spl les/R/spl les/6/7 are presented, and some of their error performances evaluated.     

Bounds on the error performance of coding for nonindependentRician-fading channels

New upper bounds on the error performance of coded systems for Rician channels are presented. The fading channels need not be fully interleaved to obtain meaningful performance results. These bounds hold for coherent, differentially coherent and noncoherent demodulation of binary signals. They provide a useful analytical approach to the evaluation of the error performance of convolutional or block coding and they may be generalized to M-ary signals and trellis modulation. The approach allows for complex bounds using the fine structure of the code, for simpler bounds similar to those on memoryless channels and finally for a random coding bound using the cutoff rate of the channel. The analysis thus permits a step by step evaluation of coded error performances for Rician-fading channels     

Further results on high-rate punctured convolutional codes forViterbi and sequential decoding

The weight spectra of high-rate lpunctured convolutional codes are evaluated under the hypothesis of a low-rate structure. This interpretation yields results slightly different from those obtained when weight spectra are evaluated assuming a true high-rate structure for punctured codes. The search for long memory punctured codes is extended by providing new punctured codes of rates 4/5, 5/6, 6/7, and 7/8 with memories ranging from 9 to 19     

New VLSI architectures for fast soft-decision threshold decoders

New VLSI architectures for fast convolutional threshold decoders that process soft-quantized channel symbols are presented. The new architectures feature pipelining and parallelism and make it possible to fabricate decoders for data rates up to hundreds of Mbits per second. With these architectures, the data rate is shown to be independent of the memory of the code, implying that fast AAPP (approximate a posteriori probability) decoders can be built for long powerful codes. Furthermore, the architectures are convenient to use with low and high coding rates. Using a typical example it is shown that a soft-decision threshold decoder can provide a substantial coding gain while being less costly to implement than the hard-decision threshold decoder     

L'auto-observation et la fixation d'objectifs comme déterminants du transfert des apprentissages en formation appliquée.

Evaluated the simple and combined effects of goal setting and self-monitoring interventions on transfer of training following a course on note taking, and explored the moderating role of self-efficacy in enhancing the effects of the interventions. Following attendance in a training course, 69 college students were randomly assigned to 1 of the following groups: goal setting, self-monitoring, both goal setting and self-monitoring, or control. The actual notes taken by Ss prior to the training were compared to those taken 5 wks later. The behavioral self-monitoring manipulation was the only one which had a significant impact on transfer of training. Goal setting did not enhance performance even when combined with self-monitoring. Self efficacy was a significant predictor of note taking performance but did not moderate the effectiveness of the interventions. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

High-rate punctured convolutional codes: structure properties andconstruction technique

The authors present some properties of punctured convolutional codes, providing a construction method and a list of new, good, high-rate, long-memory punctured codes. The structure of punctured codes is examined and an upper bound on the free distance of punctured codes is derived, indicating that punctured codes are good codes. A construction method that generates the low-rate original codes which duplicate given known high-rate codes through perforation is proposed. Tables of punctured codes that duplicate the best known nonsystematic codes of rates 2/3 and 3/4 with memory lengths ranging from 3 to 23 and from 3 to 9, respectively, are given, together with the best known systematic codes for rates ranging from 2/3 to 7/8 with very long memory, M=44 through 48     

The effect of sex and emotion on selection of helping responses by peers.

52 male and 52 female undergraduates indicated the extent to which they would be likely to use different helping categories in response to tape recordings of male or female stimulus persons expressing problems in angry, sad, or neutral manners. Females indicated that they would use more nurturing responses to individuals expressing problems. Emotion expressed proved to be a very powerful determinant of indicated responses. Targets expressing their problems in a sad manner were more likely to be helped than those presenting their problems with anger or little emotion. Angry targets would receive the least amount of help and were most negatively evaluated. Target sex had little effect on helping responses or evaluations of targets. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the capacity and BER performance of multiuser scheduling over MIMO Nakagami-m fading channels

This paper presents a performance analysis for evaluating multiuser and spatial diversities achieved in multiuser MIMO systems employing orthogonal space-time block coding (OSTBC) over Nakagami-m fading channels. Two multiuser scheduling schemes are considered, absolute SNR-based scheduling (AS) and normalized SNR-based scheduling (NS) schemes for both heterogeneous and homogeneous wireless networks. Analytical expressions are derived for the average channel capacity and average bit error rate (BER) of these systems. The considered scheduling schemes are numerically evaluated and compared in terms of average capacity, average BER and fairness. It is shown that in the heterogeneous case, unlike the AS scheme, the NS scheme can guarantee fairness to the users. It is also shown that in the heterogeneous case, the AS scheme yields a higher average capacity and a lower average BER compared to the NS scheme and to the homogeneous case.     

Oxygen reduction of pre-synthesized organically capped platinum nanoparticles assembled in mixed Langmuir-Blodgett films: Evolutions with the platinum amount and leveling after fatty acid removal

Mixed Langmuir-Blodgett (LB) films based on crown derivatized platinum nanoparticles (NPs) and fatty acid showed a direct electrochemical activity toward oxygen reduction reaction (ORR) in acidic medium. This paper reports on the original and strong effects observed in the electrochemical response of these two-phase systems towards oxygen reduction by varying the Pt amount in the mixed LB films. The easy manipulation of pre-synthesized organically capped nanoparticles, combined with the features of the Langmuir-Blodgett technique allows good control of the platinum loading in the films. Pt loadings are set by changing the number of deposited monolayers and/or their nanoparticle density. Loading variations induce strong modifications in the voltammograms and are considered in terms of the relative weight of the two phases: platinum nanoparticles and fatty acids. We point out the strong influence of the environment of platinum nanoparticles towards their electrocatalytical behaviour. Various effects, such as electrical resistance of the nanostructures are considered. Evolution of the peak current density ratios from O₂ and [Fe(CN)₆]^3−/4− probes as a function of platinum loading in mixed films could suggest a possible change in the dominating number of electrons exchanged in the ORR. The effect of the fatty acid phase is definitely demonstrated by the leveling of the electrochemical responses after its elimination from the thin film structures. The electrochemical response is then likely governed by only the organic crown of the particles, which controls the ultimate local environment of the platinum particles. In such a situation, the optimized platinum loading is found to be 2.4 μg cm⁻².     

On the performance of multi‐hop wireless relay networks

User cooperation has evolved as a popular coding technique in wireless relay networks (WRNs). Using the neighboring nodes as relays to establish a communication between a source and a destination achieves an increase of the diversity order. The relay nodes can be seen as a distributed multi‐antenna system, which can be exploited for transmit diversity by using distributed space–time block coding (STBC). In this paper, we investigate the bit error rate (BER) of multi‐hop WRNs employing distributed STBC at the relay nodes. We develop the general model of WRNs using distributed STBC, and we derive the pairwise error probability and an approximation of the BER. We examine the impact of several parameters, such as distributed STBC at the relays, the number of relays, the distances between the nodes, and the channel state information available at the receivers, on the BER performance of the multi‐hop WRN. The obtained results provide guidelines about the expected error performance and the design of channel estimation for these networks. Copyright © 2011 John Wiley & Sons, Ltd.