Clemens Von Helmolt

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A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht’s integrating sphere. When a LOS(More)
A multiple-input multiple-output (MIMO) indoor radio system is studied to identify the origin of a typical performance degradation. When the data and overlay pilot-sequences for the channel estimation are transmitted at the same time, an error floor at high signal-to-noise ratio is normally observed. The floor is caused by channel estimation errors due to(More)
We study the relation between antenna spacing and capacity of MIMO channels for indoor environments using a ray tracing program. It has been confirmed also by measurements that in rich scattering environments an antenna spacing below 0.5λ is sufficient to reach nearly the full capacity predicted for multiple-antenna arrays in ideal and uncorrelated Rayleigh(More)
The implementation of adaptive channel inversion into a real-time single carrier MIMO test-bed is reported for the first time. Since no joint detection is possible at the distributed users all signal preprocessing is performed at the transmitter which adapts the transmission links to all mobile terminals adaptively depending on the actual channel situation.(More)
The theory of homogenous matrix polynomials provides a clear and powerful framework for the characterization of frequency selective multiple-input multiple-output (MIMO) channels. The concept proposed in this paper is a natural unification of methods, known from flat fading MIMO channels and frequency selective single-input single-output (SISO) channels.(More)