A macroanalysis of hsdpa receiver models

We consider high speed packet data access service (HSDPA) which is introduced with the Release-5 of UMTSFDD standard. Signal to interference + noise ratio (SINK) and throughput bounds from the usage of channel matched filter (RAKE in FIR form) and LMMSE equalizer + correlator type mobile terminal receiver structures are obtained for the high speed downlink shared channels (HSDSCHs) under certain residual intracell interference levels which represent the situations after the possible usage of front end intracell interference cancellers. Exact orthogonality factor expression is obtained which is valid for any type of linear receiver. The distributions of radio channel parameters and received powers from the own and surrounding base stations are modeled under correlated shadowing w.r.t the mobile position, the cell radius and the type of environment. From such modeling, more realistic performance figures might be obtained as compared to fixing them to certain values. © 2005 IEEE

Optimization Combined Chip and Symbol Level Equalization for Downlink WCDMA Reception

We consider iterative WCDMA receiver techniques for the UMTS FDD downlink. The popular LMMSE chip equalizer-correlator receiver does not exploit subspaces in partially loaded systems. This is in contrast to the symbol level LMMSE receiver, which is time-varying though, due to the scrambler, and hence too complex to implement. A compromise can be found by performing symbol level Multi-Stage Wiener Filtering (MSWF), which is an iterative solution in which the complexity per iteration becomes comparable to twice that of the RAKE receiver. Since the MSWF works best when the input is white, better performance is obtained if the RAKE in each MSWF stage gets replaced by a chip equalizer-correlator. One of the main contributions here is to point out that the chip equalizer benefits from a separate optimization in every stage. This is shown through a mix of analysis and simulation results

Polynomial expansion WCDMA receivers refined by local MMSE functionalities Yerel MMSE İşlemleriyle İyileştirilmiş Polinom Açilimli WCDMA Alici Yapilari

UMTS-FDD mode downlink system is in practice supposed to be partially loaded due to interference limitations. In other words, some of the orthogonal codes are not used. This indicates that the system is overdetermined and there exists a noise space which can be exploited to cancel the intracell and intercell interference. However, since the scramblers that differentiates the base stations are aperiodic, so are the noise spaces, which necessitates having receiver structures that vary by symbol period. In this work, interference cancellers are obtained by the interpretations of multistage multi user detection (MUD) structures, whose time varying parts are limited to scramblers and descramblers. MUD equations are formulated from symbol level MMSE-ZF equalization followed by decorrelation among users via polynomial expansion. In the fust order, a number of receiver components are replaced by their MMSE equivalents and supplements in order to obtain better SINR figures for the user of interest. © 2004 IEEE

Binary and ternary metal complexes of Congo red with amino acids

The stability constants of the 1:1 binary complexes of Ag+, Ni2+, Co2+, Y3+ metal ions with glutamic acid (Glu), leucine (Leu) and Congo red (CR) and their HA ternary complex and the protonation constants of the ligands were determined potentiometrically at a constant ionic strength of I = 0.10 mol dm(-3) (NaClO4) in aqueous solutions at 15.0, 25.0 and 35 degrees C. The thermodynamic parameters Delta G(o), Delta H-o and Delta S-o were reported for the complex formation reactions. The enthalpy changes of all complexation are found to be negative but entropy changes positive. The driving forces for the formation of Ag-CR, Ni-CR, Co-CR are the enthalpy decreases. But the driving force for Y-CR is the entropy decreases. The driving force of Ni-Glu, Co-Glu, Ni-Leu and Co-Leu systems are about equally enthalpy decrease and entropy increase while Ag-Glu and Ag-Leu complexation are enthalpy stabilized. But, the driving force of Y-Glu and Y-Leu systems are the entropy increase. For formed ternary complexes the reactions are all enthalpy-driven. (c) 2005 Elsevier Ltd. All rights reserved

Multistage estimation of time-varying wireless channel parameters Zamanla Deǧişen Mobil Kanal Parametrelerinin Çok Aşamali Kestirimi

Estimation of time-varying channel parameters in the existence of aperiodic codes (UMTS FDD mode downlink) is considered. In the first stage, coarse FIR channel estimate is obtained in every slot via the pilot channel. In the second stage, the estimate is improved by Wiener filtering across slots, modeling the channel parameters as first order autoregressive processes with a bandwidth commensurate with the Doppler spread. This operation performs the optimal compromise between temporal decorrelation due to Doppler spread and slot-wise estimation error and it can be realized by RLS adaptive filtering. In the third stage, exploiting the finite bandwidth of the pulse shape, refined FIR channel estimate is approximated to sparse multipath model for the discrete Rake receiver. ©2004 IEEE

Adaptive Chip Level Equalization for HSDPA

We consider a chip level decision-directed NLMS equalization scheme which targets estimating the total transmitted base station chip sequence in a decision-directed manner and using it as the desired response for equalizer adaptation. For this purpose, we explicitly use only the knowledge of the user-assigned HSPDSCH codes in order to obtain reliable signal components by hard decisions. By exploiting the equivalence between the actual multirate transmission in the sense of containing multiple spreading factors and the multicode pseudo-transmission at the single HSDPA spreading level we use also the estimated pseudo-symbols of other codes via LMMSE weightings. In addition to its reasonable complexity and Max-SINR achieving performance in realistic HSDPA working regimes, the proposed scheme also has the advantage of not requiring the channel parameters. We evaluate its performance by extensive simulations vis-à-vis the Griffiths equalizer which requires channel parameters. © 2006 IEEE

Use of umbrella sampling to calculate the entrance/exit pathway for Z-pro-prolinal inhibitor in prolyl oligopeptidase

Prolyl oligopeptidase (POP), a member of the prolyl endopeptidase family, is known to play a role in several neurological disorders. Its primary function is to cleave a wide range of small oligopeptides, including neuroactive peptides. We have used force biased molecular dynamics simulation to study the binding mechanism of POP. We examined three possible binding pathways using Steered Molecular Dynamics (SMD) and Umbrella Sampling (US) on a crystal structure of porcine POP with bound Z-pro-prolinal (ZPP). Using SMD, an exit pathway between the first and seventh blade of the ß-propeller domain of POP was found to be a nonviable route. US on binding pathways through the ß-propeller tunnel and the TYR190-GLN208 flexible loop at the interface between both POP domains allowed us to isolate the flexible loop pathway as the most probable. Further analysis of that pathway suggests a long-range covariation of the interdomain H-bond network, which indicates the possibility of large-scale domain reorientation observed in bacterial homologues and hypothesized to also occur in human POP