On UWB beamforming

Ultra-Wideband (UWB) communication systems and Multi-Input-Multi-Output (MIMO) techniques rank among the few emerging key technologies in wireless communications. For that reason the marriage of these two complementary approaches should deserve attention. Apparently, the extremely large ultra-wide bandwidth creates rich multipath diversity which calls, at a first glance, additional antenna elements into question. However, another point of view is as follows. The attenuation by solid materials usually increases with increasing frequency; e.g. frequencies above, say, 10 GHz are considered to be blocked by walls etc. Since UWB can occupy more than 7 GHz of bandwidth (according to FCC regularisation) the performance of a communication link can be physically extended only by adding spatial information, i.e. multiple antennas, even if such extension may play a minor role. From this point of view UWB& MIMO presents an upper physical bound for indoor communications and is therefore at least worth to be investigated. In order to see the forest for the trees, we will focus in this limited contribution on beamforming among all alternative MIMO techniques (like space time coding or spatial multiplexing).