Energy Aware Signal Processing for Software Defined Radio Baseband Implementation

The fast pacing diversity and evolution of wireless communications require a wide variety of baseband implementations within a short time-to-market. Besides, the exponentially increased design complexity and design cost of deep sub-micron silicon highly desire the designs to be reused as much as possible. This yields an increasing demand for reconfigurable/ programmable baseband solutions. Implementing all baseband functionalities on programmable architectures, as foreseen in the tier-2 SDR, will become necessary in the future. However, the energy efficiency of SDR baseband platforms is a major concern. This brings a challenging gap that is continuously broadened by the exploding baseband complexity. We advocate a system level approach to bridge the gap. Specifically, we fully leverage the advantages (programmability) of SDR platforms to compensate its disadvantages (energy efficiency). Highly flexible and dynamic baseband signal processing algorithms are designed and implemented to exploit the abundant dynamics in the environment and the user requirement. Instead of always performing the best effort, the baseband can dynamically and autonomously adjust its work load to optimize the average energy consumption. In this paper, we will introduce such baseband signal processing techniques optimized for SDR implementations. The methodology and design steps will be presented together with 3 representative case studies in HSDPA, WiMAX and 3GPP LTE.     

A comparison analysis of prefiltering methods in space-time trellis-based reduced-state turbo-detection

In this paper, we investigate two different prefiltering strategies, i.e., multiple input multiple output (MIMO) channel shortening and MIMO whitened matched filtering, to decode iteratively a space time bit interleaved coded modulation transmitted over MIMO block fading intersymbol interference channels using a trellis-based post-detector. Indeed, resorting to such front-ends allows significant complexity gain when compared to the optimal maximum a posteriori-based turbo-receiver. While those two approaches have been exhaustively visited in the past, their fair comparison in terms of trade-off between complexity and performance has – to our knowledge – never been tackled before. This paper aims at giving some valuable insights about the respective benefits of these two prefiltering methods with respect to the channel characteristics and overall receiver complexity.     

Décodage par le treillis de codes polynomiaux: un écueil à éviter

We give a simple proof of a well known property of the maximum likelihood decoding of polynomial block codes: the systematic version of the code results in fewer decoding errors than the non systematic version. As a practical result, it is interesting to decode the systematic version of the code on the treillis of the non systematic version, because the non systematic version of the code exhibits a more regular trellis, and both version generate the same codewords.     

A transmission line model for arrays of rectangular microstrip antennas

A very efficient transmission line model for the analysis of arrays of rectangular microstrip antennas is presented. The structure of the model is discussed, and its validity is proved. This is done for the isolated microstrip antenna as well as for the coupling between antennas. Then follows a discussion of the numerical efficiency. And finally a numerical example shows the effect of mutual coupling on the impedance and radiation pattern of a 21 element Chebyshev array at different scanangles.     

Forecasting solar radiation – Preliminary evaluation of an approach based upon the national forecast database

Our objective is to develop, and undertake a preliminary evaluation of a simple solar radiation forecast model using sky cover predictions from the National Digital Forecast Database as an input. This report describes the model and presents a limited evaluation of its performance against ground-measured and satellite-derived irradiances in Albany, New York.     

Confocal Scanning Laser Microscopic Study of the RDX Defect Structure in Deformed Polymer‐Bonded Explosives

The influence of an explosion‐driven deformation on the defect structure in RDX crystals embedded in a polymer‐bonded explosive was investigated by means of confocal scanning laser microscopy. The images were compared to the defect structure in the as‐received RDX grades, embedded in an epoxy resin. In this way it is possible to qualitatively analyze the changes in defect structure of the RDX crystals that were induced by the explosion‐driven deformation. For the first time, these data therefore provide experimental confirmation of how shock waves mechanically interact with energetic crystals – a topic that, up to now, was only explored by means of simulations.     

Investigation of the Failure Mechanism of HTPB/AP/Al Propellant by In‐situ Uniaxial Tensile Experimentation in SEM

The failure mechanism of a propellant consisting of hydroxyl terminated poly‐butadiene filled with ammonium perchlorate and aluminum (HTPB/AP/Al) was determined by performing in‐situ uniaxial tensile tests in a scanning electron microscope (SEM). The experimental test plan contained uniaxial tensile test experiments performed at room temperature (25 °C) at three different strain rates (30, 150 and 750 μm min⁻¹). The in‐situ images and in‐situ videos collected by the SEM were correlated with the stress‐strain diagrams created with the tensile experiments, in order to relate the failure mechanism to the features found in the stress‐strain diagram. No significant strain rate dependency of the failure mechanism was observed when working with strain rates up to 750 μm min⁻¹ and working at room temperature. The stress‐strain diagram showed indications of existing cracks and voids opening up prior to the creation of new cracks and/or voids in the sample, debonding of binder with AP particles as well as nucleation and coalescence of voids. On the fracture surfaces of the samples, it was apparent that the binder cleanly separated from the large AP particles but had a better bond with the aluminum particles. However, a difference in the appearance of a short drawing phase in the stress‐strain diagram of the propellant is observed at different strain rates. The presented results clearly demonstrate the major advantage of the combination of microscopic tensile tests with microscopic observations, linking the stress‐strain behavior to the mechanical deformation processes taking place in these propellant samples at the microscopic level.     

The Influence of Film Morphology in High‐Mobility Small‐Molecule:Polymer Blend Organic Transistors

Organic field‐effect transistors (OFETs) based upon blends of small molecular semiconductors and polymers show promise for high performance organic electronics applications. Here the charge transport characteristics of high mobility p‐channel organic transistors based on 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl) anthradithiophene:poly(triarylamine) blend films are investigated. By simple alteration of the film processing conditions two distinct film microstructures can be obtained: one characterized by small spherulitic grains (SG) and one by large grains (LG). Charge transport measurements reveal thermally activated hole transport in both SG and LG film microstructures with two distinct temperature regimes. For temperatures >115 K, gate voltage dependent activation energies (E_A) in the range of 25–60 meV are derived. At temperatures <115 K, the activation energies are smaller and typically in the range 5–30 meV. For both film microstructures hole transport appears to be dominated by trapping at the grain boundaries. Estimates of the trap densities suggests that LG films with fewer grain boundaries are characterized by a reduced number of traps that are less energetically disordered but deeper in energy than for small SG films. The effects of source and drain electrode treatment with self‐assembled monolayers (SAMs) on current injection is also investigated. Fluorinated thiol SAMs were found to alter the work function of gold electrodes by up to ～1 eV leading to a lower contact resistance. However, charge transport analysis suggests that electrode work function is not the only parameter to consider for efficient charge injection.     

Removal of the endocrine disrupter nonylphenol and its estrogenic activity in sludge treatment processes

The estrogenic compound nonylphenol (NP) is frequently found in sludge from sewage treatment works. Hence, when sewage sludge is spread on the land, endocrine-disrupting compounds may get into the soil. The goal of this study was to investigate the extent to which aerobic mesophilic treatment in continuous reactors permits the removal of NP from sludge and how this process may be useful for treating anaerobically stabilised sludge. We also report on the behaviour of NP during the anaerobic treatment of sludge. The reduction in sludge estrogenic activity observed in the different types of treatment, as measured using estrogen-responsive reporter cells lines (MELN bioassay), was compared with NP removal rates. Under anaerobic conditions, no degradation of NP and its estrogenic activity was observed. Indeed, an accumulation of the compound occurred. In contrast, high removal of NP was achieved in aerobic conditions as well as in aerobic Post-treatment of anaerobically pre-digested sludge, with a concomitant reduction of the sludge's estrogenic potency.