3,350 research outputs found
Performance of Broadband Multicarrier DS-CDMA using Space-Time Spreading-Assisted Transmit Diversity
No full textIn this contribution multicarrier direct-sequence code-division multiple-access (MC DS-CDMA) using space–time spreading (STS)-assisted transmit diversity is investigated in the context of broadband communications over frequency-selective Rayleigh-fading channels. We consider the issue of parameter design for the sake of achieving high-efficiency communications in various dispersive environments. Furthermore, in contrast to conventional MC DS-CDMA schemes employing time (T)-domain spreading only, in this contribution we also investigate broadband MC DS-CDMA schemes employing both T-domain and frequency (F)-domain spreading, i.e., employing TF-domain spreading. The bit-error rate (BER) performance of STS-assisted broadband MC DS-CDMA is investigated for downlink transmissions associated with the correlation based single-user detector and the decorrelating multiuser detector. Our study demonstrated that when appropriately selecting the system parameters, broadband MC DS-CDMA using STS-assisted transmit diversity constitutes a promising downlink transmission scheme. This scheme is capable of supporting ubiquitous communications over diverse communication environments without BER performance degradation. Index Terms—Broadband system, code-division multiple access (CDMA), frequency-domain spreading, frequency-selective fading, multicarrier direct-sequence code-division multiple-access (MC-DS-CDMA), multicarrier CDMA, multicarrier modulation, multiuser detection, space–time spreading (STS), transmit diversity
Adaptive Minimum-BER Linear Multiuser Detection for DS-CDMA Signals in Multipath Channels
No full textThe problem of constructing adaptive minimum bit error rate (MBER) linear multiuser detectors is considered for direct-sequence code division multiple access (DS-CDMA) signals transmitted through multipath channels. Based on the approach of kernel density estimation for approximating the bit error rate (BER) from training data, a least mean squares (LMS) style stochastic gradient adaptive algorithm is developed for training linear multiuser detectors. Computer simulation is used to study the convergence speed and steady-state BER misadjustment of this adaptive MBER linear multiuser detector, and the results show that it outperforms an existing LMS-style adaptive MBER algorithm first presented at Globecom'98 by Yeh, Lopes and Barry
Measurement of the branching fractions of Ds+→η'X and Ds+→η'ρ+ in e+e-→Ds+Ds-
No full textÇetin, Serkant Ali (Dogus Author)We study Ds+ decays to final states involving the η' with a 482 pb-1 data sample collected at s=4.009 GeV with the BESIII detector at the BEPCII collider. We measure the branching fractions B(Ds+→η'X)=(8.8±1.8±0.5)% and B(Ds+→η'ρ+)=(5.8±1.4±0.4)% where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio B(Ds+→η'π+π0)<5.1% at the 90% confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of B(Ds+→η'ρ+)
SUPERSEDED - Genetic and epigenetic architectures of neurological protein biomarkers in the Lothian Birth Cohort 1936 - GWAS Proteins
No full text## THIS ITEM HAS BEEN REPLACED BY THE ONE WHICH CAN BE FOUND AT https://doi.org/10.7488/ds/2612 ##
Data supporting the paper Hillary, R, McCartney, DL, Harris, S, Stevenson, A, Seeboth, A, Zhang, Q, Liewald, D, Evans, K, Ritchie, C, Tucker-Drob, EM, Wray, NR, Mcrae, AF, Visscher, PM, Deary, I & Marioni, R 2019, 'Genome and epigenome wide studies of neurological protein biomarkers in the Lothian Birth Cohort 1936', Nature Communications, vol. 10, 3160. https://doi.org/10.1038/s41467-019-11177-x. Specifically GWAS proteins. For seven GWAS summary files, there was an incorrect number of SNPs and the files were not formatted in line with the remaining, correct summary statistics files. The dataset has therefore been superseded - the corrected dataset is available at https://doi.org/10.7488/ds/2612
The Analysis of design and manufacturing tasks using haptic and immersive VR - Some case studies
No full textThe use of virtual reality in interactive design and manufacture has been researched extensively but the practical application of this technology in industry is still very much in its infancy. This is surprising as one would have expected that, after some 30 years of research commercial applications of interactive design or manufacturing planning and analysis would be widespread throughout the product design domain. One of the major but less well known advantages of VR technology is that logging the user gives a great deal of rich data which can be used to automatically generate designs or manufacturing instructions, analyse design and manufacturing tasks, map engineering processes and, tentatively, acquire expert knowledge. The authors feel that the benefits of VR in these areas have not been fully disseminated to the wider industrial community and - with the advent of cheaper PC-based VR solutions - perhaps a wider appreciation of the capabilities of this type of technology may encourage companies to adopt VR solutions for some of their product design processes. With this in mind, this paper will describe in detail applications of haptics in assembly demonstrating how user task logging can lead to the analysis of design and manufacturing tasks at a level of detail not previously possible as well as giving usable engineering outputs. The haptic 3D VR study involves the use of a Phantom and 3D system to analyse and compare this technology against real-world user performance. This work demonstrates that the detailed logging of tasks in a virtual environment gives considerable potential for understanding how virtual tasks can be mapped onto their real world equivalent as well as showing how haptic process plans can be generated in a similar manner to the conduit design and assembly planning HMD VR tool reported in PART A. The paper concludes with a view as to how the authors feel that the use of VR systems in product design and manufacturing should evolve in order to enable the industrial adoption of this technology in the future
Groupwise Multiuser Detection in a Multirate DS-CDMA System
No full textThis report presents the performance of groupwise successive interference cancellation (GSIC) within a direct sequence code division multiple access system (DS-CDMA). Within the groups, matched filter and PIC receivers are used for detection of the users. A multirate DS-CDMA system model, based on a single rate system is presented. Although the study of multiuser detection for single rate systems has resulted in several structures, multiuser receivers designed specifically for a DS-CDMA variable spreading factor multirate system are shown to be benificial. Since they can exploit the specific properties of these systems. The bit error rate performance of matched filter, parallel interference cancellation and GSIC receivers are compared in AWGN channel. The GSIC receiver is seen to perform best. The various GSIC receiver variants are then simulated in a Rayleigh fading channel to investigate how they will perform in a realistic mobile environment. Finally the impact of fixed delay is studied.Applied SciencesElectrical EngineeringTelecommunications and Traffic-Control Systems Grou
Multibeam Adaptive Antenna Array Applied to DS-CDMA Communication Systems
No full textIn this thesis, the multibeam adaptive antenna array has been investigated for application to DS/CDMA The objective is to design an adaptive controller and a beamformer for an Adaptive Antenna Array suitable for the wideband DS/CDMA environment. The research was in accordance with the current research on third generation mobile communications systems in development in Europe…Applied SciencesInformation Technology and SystemsTelecommunications and Traffic Control Systems Grou
Performance Analysis of DS, SFH and Hybrid DS/SFH CDMA in an Micro - and Macro cellular Environment with Fading and Shadowing: Task report
No full textIn this report, a performance analysis of DS, SFH and Hybrid DS/SFH in terms of biterror probability, throughput and delay are presented. The modulation techniques used are BPSK and QPSK. The effect of Selection Diversity and Forward Error Correction (FEC) Codeon the performance are also investigated. A comparison between the CDMA techniques is made in macro- and micro cellular environment.Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems Grou
Reduced-rank adaptive least bit-error-rate detection in hybrid direct-sequence time-hopping ultrawide bandwidth systems
No full textDesign of high-efficiency low-complexity detection schemes for ultrawide bandwidth (UWB) systems is highly challenging. This contribution proposes a reduced-rank adaptive multiuser detection (MUD) scheme operated in least bit-errorrate (LBER) principles for the hybrid direct-sequence timehopping UWB (DS-TH UWB) systems. The principal component analysis (PCA)-assisted rank-reduction technique is employed to obtain a detection subspace, where the reduced-rank adaptive LBER-MUD is carried out. The reduced-rank adaptive LBERMUD is free from channel estimation and does not require the knowledge about the number of resolvable multipaths as well as the knowledge about the multipaths’ strength. In this contribution, the BER performance of the hybrid DS-TH UWB systems using the proposed detection scheme is investigated, when assuming communications over UWB channels modeled by the Saleh-Valenzuela (S-V) channel model. Our studies and performance results show that, given a reasonable rank of the detection subspace, the reduced-rank adaptive LBER-MUD is capable of efficiently mitigating the multiuser interference (MUI) and inter-symbol interference (ISI), and achieving the diversity gain promised by the UWB systems
Search for the W-exchange decays B-0 -> Ds(*)-Ds(*)+
No full textWe report a search for the decays B-0-> Ds-Ds+, B-0-> Ds*-Ds+, and B-0-> Ds*-Ds*+ in a sample of 232x10(6) Upsilon(4S) decays to B (B) over bar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) storage ring. We find no significant signal and set upper bounds for the branching fractions: B(B-0-> Ds-Ds+) Ds*-Ds+) Ds*-Ds*+)< 2.4x10(-4) at 90% confidence level
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