On the SNR penalty of MPSK with hybrid selection/maximal ratio combining over i.i.d. Rayleigh fading channels

Closed-form expressions that lower and upper bound the penalty of hybrid selection/maximal ratio combining relative to maximal ratio combining (MRC) for M-ary phase-shift keying (MPSK) modulation are proved. The bounds offer simple-to-evaluate explicit expressions, and are typically within 0.6 dB for hybrid systems with diversity order up to eight that use at least two branches, yet are independent of signal-to-noise ratio (SNR). Contrary to conclusions conjectured in a previously published paper, it is proved that the SNR penalty is not a constant, independent of SNR. It is also shown that previous estimates of the performance losses of selection diversity relative to MRC underestimate or lower bound the losses for MPSK modulation systems, and that the true loss can be significantly larger than previously believed. An upper bound to this loss is also obtained.     

Techniques for high-speed implementation of nonlinear cancellation

The authors present techniques for breaking the bottleneck caused by delays in the feedback loop, which can severely limit the maximum data rate of a detector, operating with nonlinear cancellation (NLC). The authors first show how to simplify the loop to avoid high-speed switching of analog signals by using multiple decision elements, each with a different threshold level. The authors then show how to use lookahead computation to increase the delay permissible in the feedback loop. The authors describe nonlinear cancellation, and outline some of the problems of implementing NLC at high data rates. Techniques for overcoming these problems are developed and are illustrated with the example of a simple one-tap NLC. The authors describe how to generalize the techniques to more complex NLCs and present some more examples     

Two signaling schemes for improving the error performance of frequency division duplex (FDD) transmission systems using transmitter antenna diversity

We propose two signaling schemes that exploit the availability of multiple (N) antennas at the transmitter to provide diversity benefit to the receiver. This is typical of cellular radio systems where a mobile is equipped with only one antenna while the base station is equipped with multiple antennas. We further assume that the mobile-to-base and base-to-mobile channel variations are statistically independent and that the base station has no knowledge of the base-to-mobile channel characteristics. In the first scheme, a channel code of lengthN and minimum Hamming distanced _minN is used to encode a group ofK information bits. Channel code symbolc _i is transmitted with thei th antenna. At the receiver, a maximum likelihood decoder for the channel code provides a diversity ofd _min as long as each transmitted code symbol is subjected to independent fading. This can be achieved by spacing the transmit antennas several wavelengths apart. The second scheme introduces deliberate resolvable multipath distortion by transmitting the data-bearing signal with antenna 1, andN–1 delayed versions of it with antennas 2 throughN. The delays are unique to each antenna and are chosen to be multiples of the symbol interval. At the receiver, a maximum likelihood sequence estimator resolves the multipath in an optimal manner to realize a diversity benefit ofN. Both schemes can suppress co-channel interference. We provide code constructions and simulation results for scheme 1 to demonstrate its merit. We derive the receiver structure and provide a bound on the error probability for scheme 2 which we show to be tight, by means of simulations, for the nontrivial and perhaps the most interesting caseN=2 antennas. The second scheme is backward-compatible with two of the proposed digital cellular system standards, viz., GSM for Europe and IS-54 for North America.     

Segregation by size difference in a conical fluidized bed of pharmaceutical granulate

Axial and radial segregation studies of a dry placebo pharmaceutical granulate exhibiting a continuous, bimodal particle size distribution have been carried out in a bench-scale conical fluidized bed. Experiments were conducted at superficial gas velocities of 0.5, 0.75, and 1.0 m/s based on the cone inlet diameter and static bed heights of 0.12 and 0.17 m above the distributor. Axial profiles of the mixing index show that granule greater than 800 μm segregate to the bottom of the bed. Radial segregation data shows that the large granule tends to accumulate at the centre bottom and becomes better mixed as the gas velocity is increased. Static bed height showed no influence on radial or axial segregation in this study. It is theorized that observed segregation patterns are because the local velocities in the dilute central core region of the conical bed are less than the terminal velocities of the largest particles in the particle size distribution.     

Tomographic reconstruction of stratified fluid flow

A method for imaging a moving fluid is proposed and evaluated by numerical simulation. A cross-section of a three-dimensional fluid is probed by high-frequency acoustic waves from several different directions. Assuming straight-ray geometric acoustics, the time of flight depends on both the scaler sound speed and the vector fluid velocity. By appropriately combining travel times, projections of both the sound speed and the velocity are isolated. The sound speed is reconstructed using the standard filtered backprojection algorithm. Though complete inversion of velocity is not possible, sufficient information is available to recover the component of fluid vorticity transverse to the plane of insonification. A new filtered backprojection algorithm for vorticity is developed and implemented. To demonstrate the inversion procedure, a 3-D stratified fluid is simulated and travel time data are calculated by path integration. These data are then inverted to recover both the scaler sound speed and the vorticity of the evolving flow.     

?Muskelaufbaupr?parate“ aus Konsumentensicht - Ergebnisse einer Verbraucherbefragung in Nordrhein-Westfalen

Supplemente für Sportler, insbesondere ,,Muskelaufbaupr?parate“, fanden bei bisher durchgeführten Erhebungen zum Konsumverhalten von Nahrungssupplementen nur wenig Beachtung. Im Hinblick auf eine effektive und zielgruppenorientierte Risikokommunikation sind Kenntnisse zum Konsumverhalten zu dieser Produktgruppe allerdings unerl?sslich. Ziel der Erhebung war es daher, im Bereich der Sportlersupplemente Erwartungen der Verwender an derartige Produkte, ihren Informationsstand sowie die Verwendungsh?ufigkeit zu untersuchen. Die Umfrage (n=145) wurde in Nordrhein-Westfalen mittels standardisierter Frageb?gen anonymisiert durchgeführt. Als Einschlusskriterien für die Studienteilnahme wurden eine sportliche Aktivit?t ≥ 2 Trainingseinheiten/ Woche mit einer Dauer von jeweils ≥ 1 Stunde sowie die Mitgliedschaft in einem Fitnessstudio und / oder Sportverein festgelegt.