3,982 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+)
‘D is for dangerous’: devolution and the ongoing decline of manufacturing in Northern England
No full textThis chapter considers the recent history, and likely future, of manufacturing in Northern England, with reference to the potential impact of initiatives related to the Northern Powerhouse agenda in this area. The chapter is structured around ‘the three Ds’ of the Northern Powerhouse: deindustrialisation, devolution and de-development. Contesting the view that the Northern Powerhouse can be understood primarily as a process of institutional or constitutional reform, it instead locates the agenda within the long (but limited) history of UK industrial policy. It argues that regional policy has always substituted for industrial policy in the UK state’s ‘horizontal’ support for manufacturing, and that devolution to Northern city-regions is therefore the ultimate expression of laissez-faire industrial policy. However, the agenda touches upon post-crisis concerns around place and empowerment, even while it serves to reduce the control of Northern citizens over their own local economies by offering only a narrow understanding of how economies develop
Spore assemblages from the Lower Devonian Xujiachong Formation from Qujing, Yunnan, China
No full texthe Lower Devonian Xujiachong Formation from the vicinity of Qujing City, Yunnan, China is interpreted as a terrestrial-fluviatile-lacustrine sequence. It contains important nonmarine biotas including plants, fish and invertebrates. The plants are particularly interesting as they include many endemic taxa. Dispersed spore assemblages have been recovered from the upper part of this formation. The spores are well preserved and of moderate thermal maturity. They are systematically described and four new species erected: Aneurospora xujiachongensis sp. nov., Chelinospora ouyangii sp. nov., Camptozonotriletes? luii sp. nov. and Leiozonospora xichongensis sp. nov. One new combination is proposed: Aneurospora conica (Ouyang and Lu) comb. nov. This is a rare report of a Lower Devonian dispersed spore assemblage from the South China Plate. Indeed, few dispersed spore assemblages of this age are known outside of Euramerica and Northern Gondwana. It is suggested that the Xujiachong Formation spore assemblages can all be equated to the polygonalis-emsiensis Spore Assemblages Biozone (PE SAB) of Richardson and McGregor (1986) indicating an early (but not earliest) Pragian to ?earliest Emsian age. However, caution is urged, because biostratigraphical interpretation is difficult owing to distinct differences between dispersed spore assemblages from South China and Euramerica/Northern Gondwana. This almost certainly reflects palaeophytogeographical variation and regional endemism among early land plant floras on widely separated land masses. Palynofacies analysis supports a nonmarine origin for the deposits of the Xujiachong Formation, with the very rare marine palynomorphs that were encountered interpreted as reworked
Supplemental Material, ds-vrd-10.1177_2474126418786659 - Longitudinal Follow-Up of Choroidal Thickness in Central Retinal Vein Occlusion With and Without Cystoid Macular Edema
No full textSupplemental Material, ds-vrd-10.1177_2474126418786659 for Longitudinal Follow-Up of Choroidal Thickness in Central Retinal Vein Occlusion With and Without Cystoid Macular Edema by Atalie C. Thompson, Akshay S. Thomas, Adam L. Rothman, Duncan Berry, and Sharon Fekrat in Journal of VitreoRetinal Diseases</p
FellWalker - a clump identification algorithm
No full textAbstractThis paper describes the FellWalker algorithm, a watershed algorithm that segments a 1-, 2- or 3-dimensional array of data values into a set of disjoint clumps of emission, each containing a single significant peak. Pixels below a nominated constant data level are assumed to be background pixels and are not assigned to any clump. FellWalker is thus equivalent in purpose to the CLUMPFIND algorithm. However, unlike CLUMPFIND, which segments the array on the basis of a set of evenly-spaced contours and thus uses only a small fraction of the available data values, the FellWalker algorithm is based on a gradient-tracing scheme which uses all available data values. Comparisons of CLUMPFIND and FellWalker using a crowded field of artificial Gaussian clumps, all of equal peak value and width, suggest that the results produced by FellWalker are less dependent on specific parameter settings than are those of CLUMPFIND
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
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