4,061 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+)
Measurement of the Ratios of Branching Fractions B(Bs0->Ds-π+π+π-)/B(B0->D-π+π+π-) and B(Bs0->Ds-π+)/B(B0->D-π+)
No full textUsing 355 pb-1 of data collected by the CDF II detector in pp̅ collisions at √s=1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B(s)0→D(s)-π+ and B(s)0→D(s)-π+π+π-. We present the first measurement of the ratio of branching fractions B(Bs0→Ds-π+π+π-)/B(B0→D-π+π+π-)=1.05±0.10(stat)±0.22(syst). We also update our measurement of B(Bs0→Ds-π+)/B(B0→D-π+) to 1.13±0.08(stat)±0.23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(Bs0→Ds-π+)=[3.8±0.3(stat)±1.3(syst)]×10-3 and B(Bs0→Ds-π+π+π-)=[8.4±0.8(stat)±3.2(syst)]×10-3
Removal of NI(II) ion in the presence of DS form waters and waste waters
No full textW pracy przeprowadzono badania nad sorpcją kompleksów jonów Ni(II) z tetrasodową solą kwasu poliasparaginowego (Baypure DS 100) jako czynnikiem kompleksującym na jonitach Lewatit MonoPlus M 800 oraz Lewatit MK-51. Proces sorpcji prowadzono metodą statyczną w zależności od czasu kontaktu faz, pH, temperatury i stężenia jonów Ni(II) i DS w roztworze. Stwierdzono, że maksymalny procent usunięcia kompleksów Ni(II)-DS = 1:1 uzyskuje się dla w/w jonitów przy pH >7,0. Wzrost temperatury wpływa nieznacznie na efektywność sorpcji na wszystkich jonitach. Usuwanie jonów niklu(II) w obecności czynnika kompleksującego zachodzi z wyższą wydajnością na jonicie Lewatit MK-51.The paper presents the studies of sorption of the Ni(II) ions complexes with tetrasodium salt of polyaspartic acid (Baypure DS 100) as a complexing agent on the ion exchangers Lewatit MonoPlus M800 and Lewatit MK-51. The sorption process was carried out by the static method depending on the phase contact time, pH, temperature and concentration of Ni(II) ions and DS in the solution. The maximal percentage of Ni(II)-DS=1:1 complexes is obtained for the above mentioned ions at pH>7.0. The temperature increase causes insignificant decrease in sorption effectiveness on all ion exchangers. Removal of nickel(II) ions in the presence of the ion exchanger Lewatit MK-51
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
Irrigation and drainage in the new millennium
No full textPresented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.Diagnosis in water management is being supported more recently with the help of physically based numerical models simulating the water and salt balance. This paper presents computer aided water management for interpretation of field experiments and for predicting future scenarios. An agro-hydrological model was first calibrated and validated for local conditions (Hisar, India) and subsequently used for predicting long term impacts. Various water management response indicators are used to interpret the impact of both medium (4 years experimented) and long term (next 10 years simulated) use of such saline waters on soil environment and sustainable crop production. The present simulation study showed that the prolonged use of high salinity waters (EC ≥ 7 dS/m) with normal irrigation (preplant with 8 cm canal and postplant with 6 cm saline water) in semi-arid areas should be restricted on medium to heavy textured soils because high salinity proved detrimental to relative transpiration and ultimately to the grain yield. Salinity hazard index was inflated by 92 to 146% and relative transpiration was suppressed by 40 to 60%. Consequently, simulated wheat and pearlmillet crop yields were down to 37 and 18 q/ha for 7 dS/m water and to merely 25 and 13 q/ha for 14 dS/m water during 15th simulated year, compared to 62 and 31 q/ha realized under canal water in the beginning in 1989-90. However, simulations showed that prolonged use of marginally saline water (EC = 3.5 dS/m) under normal irrigation and even of moderately saline water (EC = 7 dS/m) under heavier irrigation (12 cm canal pre- and 10 cm saline postplant water depths), on such medium to heavy textured soils, with a sub-surface drainage system, need not be forbidden. Reasonably good crop yields could still be obtained in the range of 46-48 and 21-22 q/ha for wheat and pearlmillet crops. Drainage effluent of 7.6 dS/m salinity from using 7 dS/m water continuously over 14 years indicates sustainability in using such moderate quality waters. But for highly saline waters (EC ≥ 14 dS/m) such long term usage needs to be restricted on such soils in semi-arid areas where even the heavier amounts of irrigation failed to depress salinity hazard and elevate crop transpiration to any noteworthy levels, grain yields remaining below 30 and 15 q/ha for the two crops
Measurement of the Ratios of Branching Fractions B(Bs0?Ds-?+)/B(B0?D-?+) and B(B+?D?0?+)/B(B0?D-?+)
No full texte report an observation of the decay Bs0→Ds-π+ in pp̅ collisions at √s=1.96 TeV using 115 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83±11(stat) Bs0→Ds-π+ candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a pp̅ collider. We present the first measurement of the relative branching fraction B(Bs0→Ds-π+)/B(B0→D-π+)=1.32±0.18(stat)±0.38(syst). We also measure B(B+→D̅ 0π+)/B(B0→D-π+)=1.97±0.10(stat)±0.21(syst), which is consistent with previous measurements
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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