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Smørumnedre, Denmark

Ostergaard J.,University of Aalborg | Quevedo D.E.,University of Newcastle | Jensen J.,Oticon
IEEE Transactions on Signal Processing | Year: 2011

A novel scheme for perceptual coding of audio for robust and real-time communication is designed and analyzed. As an alternative to PCM, DPCM, and more general noise-shaping converters, we propose to use psychoacoustically optimized noise-shaping quantizers based on the moving-horizon principle. In moving-horizon quantization, a few samples look-ahead is allowed at the encoder, which makes it possible to better shape the quantization noise and thereby reduce the resulting distortion over what is possible with conventional noise-shaping techniques. It is first shown that significant gains over linear PCM can be obtained without introducing a delay and without requiring postprocessing at the decoder, i.e., the encoded samples can be stored as, e.g., 16-bit linear PCM on CD-ROMs, and played out on standards-compliant CD players. We then show that multiple-description coding can be combined with moving-horizon quantization in order to combat possible erasures on the wireless link without introducing additional delays. © 2011 IEEE. Source

Zhao A.,Nokia Inc. | Ollikainen J.,Nokia Inc. | Thaysen J.,ReSound | Bodvarsson T.,Oticon
Microwave and Optical Technology Letters | Year: 2010

By splitting the upper printed wiring board (PWB) of a fold mobile phone into two parts and connected with an inductor, the near field electromagnetic scattering of mobile phones can be significantly reduced. In fact, the gap between the split PWB tends to act as a capacitor. Hence, the gap and the inductor form an LC band-stop filter embedded in the PWB. With the help of this filter, the current flowing on the PWB can be constrained before it reaches the end of the PWB, which results in less electromagnetic field scattering in the hearing aid compatibility (HAC) region, and thus, leads to an HAC compatible mobile phone design. The design principle works well for fold phones with both one-hinge and two-hinge cases. © 2010 Wiley Periodicals, Inc. Source

Liu W.,Oticon | Nannarelli A.,Technical University of Denmark
IEEE Transactions on Computers | Year: 2012

Although division and square root are not frequent operations, most processors implement them in hardware to not compromise the overall performance. Two classes of algorithms implement division or square root: digit-recurrence and multiplicative (e.g., Newton-Raphson) algorithms. Previous work shows that division and square root units based on the digit-recurrence algorithm offer the best tradeoff delay-area-power. Moreover, the two operations can be combined in a single unit. Here, we present a radix-16 combined division and square root unit obtained by overlapping two radix-4 stages. The proposed unit is compared to similar solutions based on the digit-recurrence algorithm and it is compared to a unit based on the multiplicative Newton-Raphson algorithm. © 1968-2012 IEEE. Source

Liu W.,Oticon | Calimera A.,Polytechnic University of Turin | MacIi A.,Polytechnic University of Turin | MacIi E.,Polytechnic University of Turin | And 2 more authors.
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems | Year: 2013

With the continuing scaling of CMOS technology, on-chip temperature and thermal-induced variations have become a major design concern. To effectively limit the high temperature in a chip equipped with a cost-effective cooling system, thermal specific approaches, besides low power techniques, are necessary at the chip design level. The high temperature in hotspots and large thermal gradients are caused by the high local power density and the nonuniform power dissipation across the chip. With the objective of reducing power density in hotspots, we propose two placement techniques that spread cells in hotspots over a larger area. Increasing the area occupied by the hotspot directly reduces its power density, leading to a reduction in peak temperature and thermal gradient. To minimize the introduced overhead in delay and dynamic power, we maintain the relative positions of the coupling cells in the new layout. We compare the proposed methods in terms of temperature reduction, timing, and area overhead to the baseline method, which enlarges the circuit area uniformly. The experimental results showed that our methods achieve a larger reduction in both peak temperature and thermal gradient than the baseline method. The baseline method, although reducing peak temperature in most cases, has little impact on thermal gradient. © 1982-2012 IEEE. Source

Ostergaard J.,University of Aalborg | Heusdens R.,Technical University of Delft | Jensen J.,Oticon
IEEE Transactions on Information Theory | Year: 2010

This paper is about the design and analysis of an index-assignment (IA)-based multiple-description coding scheme for the n-channel asymmetric case. We use entropy constrained lattice vector quantization and restrict attention to simple reconstruction functions, which are given by the inverse IA function when all descriptions are received or otherwise by a weighted average of the received descriptions. We consider smooth sources with finite differential entropy rate and MSE fidelity criterion. As in previous designs, our construction is based on nested lattices which are combined through a single IA function. The results are exact under high-resolution conditions and asymptotically as the nesting ratios of the lattices approach infinity. For any n, the design is asymptotically optimal within the class of IA-based schemes. Moreover, in the case of two descriptions and finite lattice vector dimensions greater than one, the performance is strictly better than that of existing designs. In the case of three descriptions, we show that in the limit of large lattice vector dimensions, points on the inner bound of Pradhan can be achieved. Furthermore, for three descriptions and finite lattice vector dimensions, we show that the IA-based approach yields, in the symmetric case, a smaller rate loss than the recently proposed source-splitting approach. © 2006 IEEE. Source

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