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Vanwinckelen G.,Catholic University of Leuven | Van Otterlo M.,Catholic University of Leuven | Driessens K.,Maastricht University | Pollin S.,Interuniversity Micro Electronics Center
2011 IEEE International Symposium on Dynamic Spectrum Access Networks, DySPAN 2011 | Year: 2011

An important aspect of spectrum sharing is reliable protection of licensed, primary, users from interference by unlicensed, secondary, users. In this paper we investigate the reliability of the iterative power adjustment algorithm proposed by Pollin, Adams and Bahai (2008). The goal of this transmission power control algorithm is to allow a static secondary transmitter to maximize its power without interfering with primary users. A distributed flooding algorithm is used to detect primary users and estimate the distance to the primary propagation contour. The secondary transmitter makes a local channel estimation with a moving least squares algorithm to average out noise. The metric used to estimate interference is the propagation contour-contour distance between the secondary and primary transmitters. In our first contribution we investigate the reliability of this metric by computing the location probability, a new FCC proposed metric for configuring Digital Terrestrial Television networks. We show that the propagation contour-contour distance is correlated with the location probability. In a second contribution we make the flooding algorithm more cost efficient by reducing communication. We then study the influence of the number of flooding messages on the performance of the iterative power adjustment algorithm in terms of location probability and number of iterations. © 2011 IEEE. Source

Lee B.G.,IBM | Schow C.L.,IBM | Rylyakov A.V.,IBM | Van Campenhout J.,IBM | And 9 more authors.
Journal of Lightwave Technology | Year: 2011

A custom 90-nm bulk digital CMOS switch driver is codesigned and integrated with a silicon photonic switch. A photonic device model is created within the electronic design environment, facilitating driver optimization and performance evaluation prior to fabrication. The fabricated drivers implemented in two variations produce transition times as low as 50 ps and generate open eye diagrams using supply voltages ranging from 0.8 to 5 V. The driver is hybrid integrated with a broadband low-power silicon photonic 2 × switch, based on a modified Mach-Zehnder interferometer. The switch has demonstrated operation over 100 nm of spectral bandwidth with less than-17-dB crosstalk, greater than 25 °C tolerance to temperature variations, and compatibility with 1-V driving signals. The integration demonstrates the interoperability of the switch and driver, which together achieve transition times below 4 ns and average power consumption of 2 mW. Finally, throughput bandwidth of 160 Gb/s is demonstrated for all switch configurations via eye diagrams and bit error rate curves. © 2011 IEEE. Source

Redant T.,Catholic University of Leuven | Dehaene W.,Catholic University of Leuven | Dehaene W.,Interuniversity Micro Electronics Center
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2013

This brief presents an approach to compensate time-of-arrival (ToA) estimation errors caused by the effect of signal depending propagation delays in receivers for ranging applications. As a straightforward reasoning, reducing the ToA error results in increased power consumption in the analog-frontend blocks of such receivers. In the proposed system topology, the asynchronous receiver's analog-front-end blocks contain an array of identical continuous-time comparators, which makes it suitable for a joint modeling approach and today's low-supply voltages. Attention is paid to tuning the nonstrobed comparator topology to make it suitable for this joint modeling. Using the comparator model in a least-squares-based algorithmic approach can reduce the ToA error (accuracy improvement) to nearly zero. A ToA systematic error reduction of 28 is faced for the ToA figure. Furthermore, energy consumption is more related to the activity of the ranging events, which makes this an interesting approach for ranging measurement rates of less than 1 MHz. © 2013 IEEE. Source

Horlin F.,Roosevelt University | Fickers J.,Roosevelt University | Emplit P.,Roosevelt University | Bourdoux A.,Interuniversity Micro Electronics Center | Louveaux J.,Catholic University of Louvain
Optics Express | Year: 2013

In order to improve the spectral efficiency of coherent optical communication systems, it has recently been proposed to make use of the orthogonal frequency-division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). Multiple optical channels spaced in the frequency domain by the symbol rate can be transmitted orthogonally, even if each channel overlaps significantly in frequency with its two adjacent channels. The solutions proposed until now in the literature unfortunately only address a single polarization communication, and therefore do not benefit from the capacity gain reached when two polarizations are used to transmit independent information signals. The aim of the present paper is to propose a receiver architecture that can decouple the two polarizations. We build an equalizer per channel at twice the symbol rate and optimize it based on the minimum mean square error (MMSE) criterion. We demonstrate the efficiency of the resulting system compared to the Nyquist wavelength-division multiplexing (N-WDM) system both in terms of performance and complexity. We also assess the system sensitivity to transmit synchronization errors and show that system can even work under significant synchronization errors. © 2013 Optical Society of America. Source

Redant T.,Catholic University of Leuven | Daniels J.,Catholic University of Leuven | Steyaert M.S.J.,Catholic University of Leuven | Dehaene W.,Catholic University of Leuven | Dehaene W.,Interuniversity Micro Electronics Center
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2011

A pulse digitizing approach for time-of-arrival pulse radio based ranging is introduced. It is based on a bank of time-to-digital converter (TDC) cores. A comparator bank triggers these multiple TDCs. This multiple event approach has advantages over classic single TDC solutions when facing unknown channel gains, noise corruption, and strong fading channel behavior. Pulses are digitized in a way that is superior in terms of performance versus power to classic A/D conversion. A power effort figure ξ and a new SNDR metric are introduced, easing performance comparison of pulse digitizers. A low power 8 channel digitizing system with a resolution of δtring=62.5ps is presented for a cm accurate ranging application. The asynchronous, event-based nature of the architecture requires nonstrobed comparators to fire value crossing events. A dynamic range of 800:1 is realized. The digitization device is designed for 130 nm standard CMOS. An analog-baseband front-end I-Q energy detection and comparator threshold level configuration D/As are added to the design. The complete system is designed to consume 4 mW. © 2011 IEEE. Source

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