Clemens Von Helmolt

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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(More)
—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)
—In future wireless networks, cooperation between the base stations may reduce the effects of intercell interference and enhance the capacity per cell. In this paper, the potential of such cooperation is evaluated using measurements of the information-theoretic channel capacity at 5.2 GHz in 4 overlapping urban microcells with 5 users. In each link, a(More)