4,573 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+)
Search for tetraquark states Xcc s- s- in Ds+ Ds+ (Ds∗+ Ds∗+) final states at Belle
No full textA search for double-heavy tetraquark state candidates Xccs ̄s ̄ decaying to Ds+Ds+ and Ds∗+Ds∗+ is presented for the first time using the data samples of 102×106 Υ(1S) and 158×106 Υ(2S) events, and the data samples at s=10.52, 10.58, and 10.867 GeV corresponding to integrated luminosities of 89.5, 711.0, and 121.4 fb-1, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. The invariant-mass spectra of the Ds+Ds+ and Ds∗+Ds∗+ are studied to search for possible resonances. No significant signals are observed, and the 90% confidence level upper limits on the product branching fractions [B(Υ(1S,2S)→Xccs ̄s ̄+anything)×B(Xccs ̄s ̄→Ds+Ds+(Ds∗+Ds∗+))] in Υ(1S,2S) inclusive decays and the product values of Born cross section and branching fraction [σ(e+e-→Xccs ̄s ̄+anything)×B(Xccs ̄s ̄→Ds+Ds+(Ds∗+Ds∗+))] in e+e- collisions at s=10.52, 10.58, and 10.867 GeV under different assumptions of Xccs ̄s ̄ masses and widths are obtained
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
Measurement of branching fraction of of Ds*+→ Ds+ π0 relative to Ds*+→ Ds+γ
No full textBased on 7.33 fb−1 of e+e− collision data taken at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we measure the branching fraction of Ds*+--> D+π0 relative to that of Ds*+ -->D+γ to be (6.16 pm 0.43 pm 0.18)%. The first uncertainty is statistical and the second one is
systematic. By using the world average value of the branching fraction of Ds*+--> D+e+e−, we determine ss
the branching fractions of Ds*+--> D+γ and Ds*+--> D+π0 to be (93.57 0.38 0.22Þ% and (5.76 0.38 0.16Þ%, respectively
Leptotrombidium cuonae Wang, Pan and Yan 1996
No full text63. Leptotrombidium cuonae Wang, Pan and Yan, 1996 Leptotrombidium (Leptotrombidium) cuonae Wang, Pan and Yan, 1996 (source not found; cited by Li, Wang & Chen 1997); Li, Wang & Chen 1997: 119, fig. 2-1-20. Diagnosis. fPp = N/N/BNN; Pc = 3; Gn = 2; fSc: AM> PL> AL; SB-PL; fCx = 1.1.1; fSt = 2.2; fD = 2H-8-6-6-6- 4-2; DS = 34; VS = 28; NDV = 62; Ip = 758; AW 75, PW 87, SB 34, ASB 28, PSB 19, SD 47, AP 26, AM 62, AL 38, PL 55, S -, H -, D min -, D max -, V min -, V max -, pa 251, pm 234, pp 273. Type data. China, Xizang Autonomous Region, Cona County, Gongri, from Niviventer eha (Wroughton). Remarks. Described from a single specimen.Published as part of STEKOLNIKOV, ALEXANDR A., 2013, Leptotrombidium (Acari: Trombiculidae) of the World , pp. 1-173 in Zootaxa 3728 (1) on page 51, DOI: 10.11646/zootaxa.3728.1.1, http://zenodo.org/record/526773
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
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