4,622 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
Multiuser Decorrelating Based Long-Range Frequency-Domain Channel Transfer Function Prediction in Multicarrier DS-CDMA Systems
No full textIn this contribution, multiuser decorrelating based frequency-domain channel estimation and long range channel prediction techniques are proposed for a generalized Multicarrier DS-CDMA (MC DS-CDMA) system communicating over a fast fading and frequency selective channel. In the MC DS-CDMA system considered, the channel transfer function (CTF) is estimated in the frequency-domain with the aid of pilot symbols by invoking the multiuser decorrelating based channel estimation technique, in order to reduce the effects of both the Multiuser Interference (MUI) and the background noise. Then, Kalman filter assisted long-range channel prediction is carried out with the aid of both the current and previous frequency-domain CTFs for the sake of predicting the future CTFs. Furthermore, a sinc-interpolator is employed for the sake of deriving the frequency-domain CTFs associated with the data symbols. Our simulation results show that for a reasonable signal-to-noise ratio (SNR) value the proposed frequency-domain multiuser decorrelating based channel estimator is robust to the effects of both the MUI as well as the noise
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+)
Heavy-light (unequal-mass) mesons light-front wave functions
No full textThe light-front wave functions for the bound states provide access to a wealth of experimental observables. We present the unequal-mass meson systems (including Bc, Bs, Bu, Ds, and Du) light-front wave functions obtained within the basis light-front quantization approach in Phys.Rev.D 98 (2018) 11, 114038 and Eur.Phys.J.C 80 (2020) 6, 522
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
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