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The paper gives an overview on trends in mobile communications which is currently one of the most emerging markets. The demand for new and extended services is a driving force for the development of future mobile networks. Especially the provision of video communications is a great challenge. The current status of MPEG and ITU-T/SG15 concerning mobile communications is described and related to current projects. In the second part some aspects for the design of video codecs for mobile video telephony are outlined. Based on the coming standard H.26P an advanced video codec is described and its suitability for mobile networks is proven by some simulation results.

Abstract-Quadtree-like pyramids have the advantage of resulting in a multiresolution representation where each pyramid node has four unambiguous parents. Such a centered topology guarantees a clearly defined up-projection of labels. This concept has been successfully and extensively used in applications of contour detection, object recognition and segmentation. Unfortunately, the quadtree-like type of pyramid has poor approximation powers because of the employed piecewise-constant image model. This paper deals with the construction of improved centered image pyramids in terms of general approximation functions. The advantages of the centered topology such a symmetry, consistent boundary conditions and accurate up-projection of labels are combined with a more faithful image representation at coarser pyramid levels. We start by introducing a general framework for the design of least squares pyramids using the standard filtering and decimation tools. We give the most general explicit formulas for the computation of the filter coefficients by any (well behaving) approximation function in both the continuous (L2) and the discrete (l2) norm. We then define centered pyramids and provide the filter coefficients for odd spline approximation functions. Finally, we compare the centered pyramid to the ordinary one and highlight some applications.

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