Error probability of coherent detection for trellis-coded partialresponse CPM on Rician fading channels

Trellis-coded continuous phase modulation (TC-CPM) schemes are attractive for bandwidth and power limited communication systems such as mobile satellite communications and land mobile radio communications. A coherent receiver for interleaved partial response TC-CPM is derived. A true upper bound on the bit error probability for flat fading channels is derived by showing that TC-CPM is equivalent to a trellis-coded modulation scheme. The upper bound is evaluated by defining an error-state diagram along with a set of characteristic distances and then applying transfer function bounding techniques. Comparison with simulation results shows the upper bound tight to within 1.5-2 dB     

Convergence behavior of iterative phase synchronization and detection

Serially concatenated systems with rotational invariance (RI-SCS) can tolerate certain phase ambiguities and, therefore, for these systems coherent detection is robust even when cycle slipping, false-lock and hangup exist during phase synchronization. However, the convergence behavior of iterative phase synchronization and detection is still not well-understood. In this paper, we present a simplified phase model to analyze the convergence of iterative receivers with/without occurrence of phase rotations. Particularly, an oscillatory convergence behavior due to cycle slipping is explained by means of density evolution. Moreover, based on per-survivor processing (PSP) and single-estimator processing (SEP) techniques, a family of adaptive soft-input soft-output algorithms are employed to implement joint phase tracking and demodulation in the context of maximum a posteriori symbol detection. Both analytical and simulation results show that for RI-SCS the convergence performance of the SEP method is more robust than that of the PSP method when carrier phase has high and random dynamics.     

Soft-limiter RAKE receivers for coded DS/DPSK systems over pulsejammed multipath-fading channels

Two soft-limiter RAKE receivers are evaluated for coded direct-sequence/differential phase shift keying (DS/DPSK) signaling over a pulse jammed multipath-fading channel that use a combination of antenna and multipath diversity. One uses predetection selective (antenna) combining followed by postdetection equal gain (multipath) combining, and the other uses postdetection equal gain combining only. In either case, the postdetection diversity combiner output is soft-limited prior to decoding. It is shown that for increasing levels of diversity the soft-limiter becomes quite effective, resulting in a receiver performance that approaches a maximum likelihood (ML) soft decision receiver with perfect jammer state information     

ACOUSTIC STUDIES OF INTERFACIAL EFFECTS IN AIRLIFT REACTORS

Rational design of airlift reactors for the culture of plant and animal cells is impeded by a lack of understanding of the causes of loss of viability. Some recent speculations in the literature suggest that gas-liquid interfacial phenomena have played prominent roles in observed instances of loss of viability in both insect and animal cell cultures. The important interfacial events may include bubble formation and detachment at the sparger, bubble coalescence and breakage, and bubble disengagement at the free surface-entailing film thinning, film rupture, and film droplet ejection.

We have carried out an experimental investigation of interfacial phenomena using macrovideography and acoustic signals recorded at both the sparger and the free surface. Data have been collected for several liquid media including distilled water, distilled water with electrolyte (NaCl), and aqueous solutions of glycerol (μ = 3 to 9.5 cP). The studies were conducted in a 3-liter, acrylic plastic, split-column airlift reactor, and air was introduced through interchangeable sieve plates (with hole diameters of 1, 2, and 3 mm). Time-series data collected from the microphone were processed for mean and root-mean-square values, and Fourier transforms were computed to identify important signal energies. A sequence of experiments was also conducted that was designed to relate specific interfacial phenomena to the frequencies of the noises produced.     

Error probability for reduced-state sequence estimation

The performance of ideal reduced-state sequence estimation (RSSE) (without error propagation) is known as a good approximation to the performance of real RSSE. In the literature, the minimum distance of ideal RSSE has been employed for approximating the error probability of real RSSE. However, this approximation can be very poor, even though the system has a large signal-to-noise ratio. In this work, a union upper bound on the error probability for ideal RSSE is used to approximate the true error probability. This union bound provides a better approximation than the minimum distance. A new method based on a stack algorithm and a subset-error state diagram is proposed for calculating this union bound. The stack algorithm is employed because it provides a good tradeoff between computer memory and computing time     

Exact cochannel interference analysis for log-normal shadowedRician fading channels

An exact analytical method is presented for evaluating the probability of cochannel interference for Rician/Rayleigh faded channels with log-normal shadowing. The method requires that at least one signal (desired or interfering) be Rayleigh faded and log-normal shadowed. The Rice factor of the desired signal is shown to have a large effect on the probability of cochannel interference, while the Rice factors of the interfering signals are shown to have little effect     

A large area liquid scintillation multiphoton detector

A 60 layer lead-liquid scintillator shower detector, which we call the SLIC, has been used for multiphoton detection in the Fermilab tagged photon spectrometer. The detector has an unimpeded active area which is 2.44 m by 4.88 m and is segmented, by means of teflon coated channels, into 3.17 cm wide strips. The 60 layers in depth are broken into three directions of alternating readouts so that three position coordinates are determined for each shower. At present the readouts are made by 334 photomultiplier tubes coupled to BBQ doped wavelength shifter bars which integrate the entire depth of the detector. It is relatively straightforward to increase the number of readouts to include longitudinal segmentation and to increase the segmentation of the outer region which are at present read out two strips to a readout. The energy and position resolutions of isolated showers are about and 3 mm., respectively. The SLIC has been used to study the K⁻π⁺π⁰ decay of the D⁰ [1], as well as for electron and muon identification in ψ → e⁺e⁻ and ψ → μ⁺μ⁻ plus π⁰ identification in γp → ψχ [8].     

Efficient sample rate conversion for software radio systems

An efficient sample rate conversion (SRC) method for software radio (SWR) systems is proposed. The proposed method modifies conventional single- or multistage SRC processes such that the computation of the output of a particular stage is performed in a hierarchical fashion. This SRC method consumes fewer computations than traditional SRC methods over a range of SRC factors and is especially suitable for SWR base station transmitters. The computational requirements of the proposed SRC method and conventional SRC methods are compared and simulation results of the proposed method are discussed.     

An adaptive rate algorithm for FH/BFSK signaling

The authors present a feedback rate control technique for FH/BFSK (frequency-hop/binary phase-shift keying) signaling over a jammed flat-flat fading channel. An algorithm is developed for tracking the channel fade level, dynamically adjusting the transmitted data rate, and mitigating the effects of partial-band noise jamming. Simulation studies indicate that improvements of about 2 dB can be obtained in the coded performance with the proposed adaptive rate system, when compared to a nonadaptive system operating over the same communication medium with identical power and bandwidth resources     

A comparison of statistical methods for estimation of less than detectable ionising radiation exposures

Methods were developed to estimate the ionising radiation dose below the detection level (DL) of personal monitoring devices for a case-control study of protracted radiation exposure and lung cancer. Exposure data were grouped by dosemeter type and monitoring period. Each group contained dosimetry data that were interval-censored from limitations in measurement precision and included left-censoring of observations below detection. The grouped data were fit to a three parameter hybrid-lognormal distribution by maximum likelihood estimation. Using the fitted distribution, bootstrap samples were either simulated by Monte Carlo or constructed by sampling with replacement. The resulting bootstrap sample distributions were then used to predict the missing dose values and the associated uncertainty in the estimate. Among study subjects, 1357 workers were monitored with film dosimetry. Among the 39,263 dose observations 20,416 were recorded as zero dose, indicating 52% left-censoring. The statistical methods estimated 0.31 person-Sv below the DL or approximately 1% of the total collective dose for this study population.