Baseband and audio mixed-signal front-end IC for GSM/EDGE applications

A complete mixed-signal front-end CMOS chip is presented, supporting GSM/EDGE as well as enhanced audio applications. The chosen solution for the transmit section is based on Laurent's approximation of the nonlinear GMSK modulator. This enables burst shaping in the I/Q domain thereby solving the problem of power ramping. Also, up to GPRS class 12 is supported. The receive section on the other hand consists of a low power dual mode continuous-time /spl Sigma//spl Delta/ ADC for I and Q, supporting ZIF and LIF modes of operation and achieving typically 12.5 bit of resolution under production conditions. An on-chip PLL, which supplies all blocks with various clock frequencies, additionally supports clock jitter suppression. The audio section comprises a codec supporting standard formats such as IIS and PCM. It features mono/stereo signaling from various sources in 16bit quality as well as high-drive buffers for 4 /spl Omega/ single-ended loads (capacitively coupled). The whole chip is powered from a 1.5/2.65 V supply voltage and consumes 22 mW in paging mode.     

Distributed space-time block coding

In this paper, a new class of distributed space-time block codes (DSTBCs) is introduced. These DSTBCs are designed for wireless networks which have a large set of single-antenna relay nodes /spl Nscr/, but at any given time only a small, a priori unknown subset of nodes S/spl sube//spl Nscr/ can be active. In the proposed scheme, the signal transmitted by an active relay node is the product of an information-carrying code matrix and a unique node signature vector of length N/sub c/. It is shown that existing STBCs designed for N/sub c/2 co-located antennas are favorable choices for the code matrix, guaranteeing a diversity order of d=min{N/sub S/,N/sub c/} if N/sub S/ nodes are active. For the most interesting case, N/sub S//spl ges/N/sub c/, the performance loss entailed by the distributed implementation is analytically characterized. Furthermore, efficient methods for the optimization of the set of signature vectors are provided. Depending on the chosen design, the proposed DSTBCs allow for low-complexity coherent, differential, and noncoherent detection, respectively. Possible applications include ad hoc and sensor networks employing decode-and-forward relaying.     

Neue Entwicklungen zur Herstellung von Hartstoffschichten mittles Plasma-CVD

New Developments in Preparation of Hard Material Coatings by Plasma CVD In this paper, the technique for the preparation of hard material coatings using a D.C. Plasma is described. Two methods are used: One is direct current (D.C.) non-pulsed glow discharge method and the other is pulsed D.C. glow discharge method. It has been shown that the temperature in chemical vapour deposition (CVD) of TiN can be reduced from about 1000°C in conventional CVD to about 500–600°C by the application of a D.C. non-equilibrium plasma. Emphasis is placed on the new design concept for industrial application by using a pulsed D.C. power source and auxiliary heating device. The structures of the TiN coatings obtained at 600 °C are analysed by means of electron microscope and X-ray diffraction methods. The film deposition rate is 1–3 μm/h. It is concluded that plasma assisted CVD of hard material coatings offers a superior alternative to the conventional CVD method.     

Decision-feedback differential demodulation of bit-interleavedcoded MDPSK

A novel simple receiver structure for M-ary differential phase shift keying (MDPSK) transmission over flat Rayleigh fading channels without channel state information is proposed. Convolutional codes are used for error correction and bit-interleaving as an appropriate means to combat the effects of fading, and the hard decisions of the Viterbi algorithm are fed back during the decoding process in order to improve the calculated bit metric. Iterative decoding with this decision-feedback differential demodulation, (DF-DM) results in significant power efficiency gains compared to those achieved using conventional differential demodulation, while the computational complexity remains low     

Fine-needle aspiration cytology of lymphoid lesions of the salivary gland: a review of 35 cases

OBJECTIVE: The aim of this study was to evaluate the effectiveness of fine-needle aspiration (FNA) in the diagnosis of primary lymphoid processes of the salivary gland. DESIGN: A retrospective study. METHOD: Between 1987 and 1994, 35 patients who underwent fine-needle aspiration (FNA) of the salivary gland had a diagnosis of a primary lymphoid process. Most presented with palpable parotid (28 patients) or submandibular (4 patients) gland masses which prompted a clinical diagnosis of pleomorphic adenoma. FNA was performed with immediate on-site evaluation. Flow cytometric cell-surface-marker analysis was performed in 28 of the 35 cases to determine the clonality of the B-cell proliferations. RESULTS: Sixteen cases of reactive hyperplasia and nine cases of malignant lymphoma diagnosed by FNA were confirmed by subsequent histopathologic examination. Lymphoma was confirmed in six of eight cases diagnosed as suspicious for lymphoma by FNA. Hodgkin's disease was suspected but not confirmed in one case and was diagnosed as a probable Warthin's tumour in another case. In all cases, the FNA diagnosis of either a reactive or malignant lymphoid process was unexpected and influenced the patient's further management. For patients diagnosed with an intraparotid lymph node, surgery could be deferred for a short period with the hope that the lymphadenopathy would spontaneously regress. For patients with a preoperative FNA diagnosis of lymphoma, a more limited biopsy could be performed, thereby reducing the operative risk to the patient and plans to process the tissue according to the institution's lymphoma protocol could be made. CONCLUSION: Clinically, reactive intraparotid lymph nodes and lymphomas present as parotid enlargements that are indistinguishable from pleomorphic adenomas. FNA is the only method of accurately establishing a preoperative diagnosis in these patients.     

Witterungsbeständige Kunststoffe und Textilien im Automobilbau – Korrelation zwischen Frei-und Gerätrebewitterung – Teil I

Weather-Resistant Plastics and Fabrics in Automotive Engineering – Correlation between Natural and Artificial Weathering

1 Schriftfassung eines Vortrages, gehalten am 21. März 1996 in Mannheim, VDI-K-Jahrestagung „Kunststoffe im Automobilbau”︁

– Part I Plastics and textiles used in automotive engineering are partly exposed to extreme weathering influences. These produce an ageing of the materials and components, which can become visible e. g. in the form of cracks, color changes or deformations. The first part of this report deals with climatic variables that are important for the ageing of polymer materials and the stresses on vehicle components due to climate. In the second part test methods used to prove the weathering resistance will be presented, first the natural weathering, then some short-time testing methods of artificial weathering. Further the correlation between natural and artificial weathering will be explained using selected examples.     

Low-complexity iterative demodulation for noncoherent codedtransmission over Ricean-fading channels

Power and bandwidth efficient noncoherent transmission over frequency nonselective Ricean-fading channels is studied. We propose a low-complexity receiver structure, which is very well suited to mobile communication scenarios with time-variant and nonstationary transmission channels. Applying bit-interleaved coded modulation with standard convolutional codes, substantial gains of several decibels in power efficiency compared to conventional differential detection are achieved. To obtain the novel noncoherent reception scheme, ideas of iterative decoding with hard-decision feedback and prediction-based branch metric calculation are combined and extended. Furthermore, the incorporation of combined phase and amplitude modulation for high bandwidth efficiency is focused on. The theoretical analysis of both the convergence and the achievable performance of iterative decoding are given by evaluating the corresponding prediction-error variance and the associated cutoff rate, respectively. The results from information theory are well confirmed by simulation results presented for different channel scenarios     

Student use of Facebook for organizing collaborative classroom activities

Social network sites such as Facebook are often conceived of as purely social spaces; however, as these sites have evolved, so have the ways in which students are using them. In this study, we examine how undergraduate students use the social network site Facebook to engage in classroom-related collaborative activities (e.g., arranging study groups, learning about course processes) to show how Facebook may be used as an informal tool that students use to organize their classroom experiences, and explore the factors that predict type of use. Data from two surveys (N = 302, N = 214) are used to analyze how Facebook use, social and psychological factors, self-efficacy, and types of instructor-student communication on Facebook are related to positive and negative collaboration among students. We found that predictors of Facebook use for class organizing behaviors include self-efficacy and perceived motivation to communicate with others using the site. When placed in the context of social and psychological factors, Facebook intensity did not predict either positive or negative collaboration, suggesting that how students used the site, rather than how often they used the tool or how important they felt it was, affected their propensity to collaborate.     

Curve Density Estimates

In this work, we present a technique based on kernel density estimation for rendering smooth curves. With this approach, we produce uncluttered and expressive pictures, revealing frequency information about one, or, multiple curves, independent of the level of detail in the data, the zoom level, and the screen resolution. With this technique the visual representation scales seamlessly from an exact line drawing, (for low‐frequency/low‐complexity curves) to a probability density estimate for more intricate situations. This scale‐independence facilitates displays based on non‐linear time, enabling high‐resolution accuracy of recent values, accompanied by long historical series for context. We demonstrate the functionality of this approach in the context of prediction scenarios and in the context of streaming data.     

Adaptive pulse-shaped OFDM with application to in-home power line communications

We propose an adaptive pulse-shaped orthogonal frequency division multiplexing (OFDM) scheme where the overhead and active sub-channels are adapted to jointly maximize capacity and fulfill the notching mask for coexistence with other devices operating in the same spectrum. The overhead includes the guard interval to partly compensate the channel dispersion, and the roll-off factor used by the shaping window. We show that significant gains are obtained compared to the case of using a fixed guard interval and roll-off factor. To simplify the implementation complexity we also propose to limit the amount of adaptation by deploying a finite set of overhead parameters. Numerical results are reported for typical wideband power line communication indoor channels.