Systolic arrays and stack decoding

The application of systolic priority queues to the sequential stack decoding algorithm is discussed in a review of the work of K. Yao and C. Y. Chang. Using a systolic array architecture, one can significantly improve the performance of such algorithms at high signal-to-noise ratios

Algebraic geometric codes

The performance characteristics are discussed of certain algebraic geometric codes. Algebraic geometric codes have good minimum distance properties. On many channels they outperform other comparable block codes; therefore, one would expect them eventually to replace some of the block codes used in communications systems. It is suggested that it is unlikely that they will become useful substitutes for the Reed-Solomon codes used by the Deep Space Network in the near future. However, they may be applicable to systems where the signal to noise ratio is sufficiently high so that block codes would be more suitable than convolutional or concatenated codes

Image coding by way of wavelets

The application of two wavelet transforms to image compression is discussed. It is noted that the Haar transform, with proper bit allocation, has performance that is visually superior to an algorithm based on a Daubechies filter and to the discrete cosine transform based Joint Photographic Experts Group (JPEG) algorithm at compression ratios exceeding 20:1. In terms of the root-mean-square error, the performance of the Haar transform method is basically comparable to that of the JPEG algorithm. The implementation of the Haar transform can be achieved in integer arithmetic, making it very suitable for applications requiring real-time performance

Planetary ephemerides approximation for radar astronomy

The planetary ephemerides approximation for radar astronomy is discussed, and, in particular, the effect of this approximation on the performance of the programmable local oscillator (PLO) used in Goldstone Solar System Radar is presented. Four different approaches are considered and it is shown that the Gram polynomials outperform the commonly used technique based on Chebyshev polynomials. These methods are used to analyze the mean square, the phase error, and the frequency tracking error in the presence of the worst case Doppler shift that one may encounter within the solar system. It is shown that in the worst case the phase error is under one degree and the frequency tracking error less than one hertz when the frequency to the PLO is updated every millisecond

On sampling band-pass signals

Four techniques for uniform sampling of band-bass signals are examined. The in-phase and quadrature components of the band-pass signal are computed in terms of the samples of the original band-pass signal. The relative implementation merits of these techniques are discussed with reference to the Deep Space Network (DSN)

A comparison of the fractal and JPEG algorithms

A proprietary fractal image compression algorithm and the Joint Photographic Experts Group (JPEG) industry standard algorithm for image compression are compared. In every case, the JPEG algorithm was superior to the fractal method at a given compression ratio according to a root mean square criterion and a peak signal to noise criterion

University of Amsterdam at TREC 2019:Complex Answer Retrieval Track

This paper documents the University of Amsterdam’s participation in the TREC 2019 Complex Answer Retrieval Track. This is the first year we actively participate in TREC CAR, attracted by the introduction to the limited “budget” of 20 passages per heading in the outline. We conducted initial exploratory experiments on making each heading contain a unique set of passages within the outline, and even do this hierarchical for each subtree and main title/article level, hence remove any redundancy between passages for different “queries” within the same title. We experimented with top-down and bottom-up filtering approaches. At the time of writing we are still in the process of analyzing the results. Some initial observations are the following. First, the restriction makes the task very challenging, as assigning any passage to the right heading in the outline is highly non-trivial. Qualitative analysis shows that our simple heuristics often make a different decision than the editorial judges on the heading under which a passage relevant to the title’s topic is assigned. Second, the fraction of judged and relevant passages per individual query or leave node is very small, making it hard to draw any definite conclusions on our experiments, and also resulting in a too small recall base to evaluate our non-pooled runs in a meaningful way. Third, when aggregating all qrels and runs to the title level, there is reasonable effectiveness of the underlying BM25 rankings, showing that the underlying passage ranking is not unreasonable, and that the hard and interesting problem is in the exact assignment of passages to the “right” headings

University of Amsterdam at TREC 2019:Complex Answer Retrieval Track

This paper documents the University of Amsterdam’s participation in the TREC 2019 Complex Answer Retrieval Track. This is the first year we actively participate in TREC CAR, attracted by the introduction to the limited “budget” of 20 passages per heading in the outline. We conducted initial exploratory experiments on making each heading contain a unique set of passages within the outline, and even do this hierarchical for each subtree and main title/article level, hence remove any redundancy between passages for different “queries” within the same title. We experimented with top-down and bottom-up filtering approaches. At the time of writing we are still in the process of analyzing the results. Some initial observations are the following. First, the restriction makes the task very challenging, as assigning any passage to the right heading in the outline is highly non-trivial. Qualitative analysis shows that our simple heuristics often make a different decision than the editorial judges on the heading under which a passage relevant to the title’s topic is assigned. Second, the fraction of judged and relevant passages per individual query or leave node is very small, making it hard to draw any definite conclusions on our experiments, and also resulting in a too small recall base to evaluate our non-pooled runs in a meaningful way. Third, when aggregating all qrels and runs to the title level, there is reasonable effectiveness of the underlying BM25 rankings, showing that the underlying passage ranking is not unreasonable, and that the hard and interesting problem is in the exact assignment of passages to the “right” headings

Integer cosine transform for image compression

This article describes a recently introduced transform algorithm called the integer cosine transform (ICT), which is used in transform-based data compression schemes. The ICT algorithm requires only integer operations on small integers and at the same time gives a rate-distortion performance comparable to that offered by the floating-point discrete cosine transform (DCT). The article addresses the issue of implementation complexity, which is of prime concern for source coding applications of interest in deep-space communications. Complexity reduction in the transform stage of the compression scheme is particularly relevant, since this stage accounts for most (typically over 80 percent) of the computational load