Multipath beamforming for UWB: channel unknown at the receiver

We study two adaptive transmission approaches that coherently combine the energy from the first several reflected paths of the ultra-wideband (UWB) channel. Thus, the signal energy at the output of a non-adaptive correlator is enhanced. The two multipath beamforming techniques, which are applicable to the DSC-UWB system in a LOS environment, suggest selecting a multilevel spreading sequence based on the signs of the first several multipath coefficients. By employing the beamforming approach, increased fluctuations in the multipath components power, are followed by an increase in the beamforming gain over m-, and single impulse sequences.