Ultra-wideband (UWB) wireless channels provide very large diversity, but make the receiver design a demanding task as far as channel estimation and timing recovery are concerned. This paper contributes with a novel receiver structure based on the multiple symbols differential detection (MSDD) framework, which bypasses not only costly channel estimation but also relaxes the stringent requirements imposed on timing recovery. Simulation results carried out in typical dense multipath propagation scenarios verify that appealing detection performance is achieved at affordable complexity thanks to an efficient implementation based on the sphere decoding (SD) algorithm.