Orthogonally-spread block transmissions for ultra-wideband impulse radios

Differential, transmitted reference (TR) and energy detection (ED) based ultra-wideband impulse radios (UWBIR) can collect the rich multipath energy offered by UWB channels with a low-complexity receiver. However, they perform satisfactorily only when the channel induced inter-pulse interference (IPI) is negligible. This can be achieved by appending a guard interval with duration greater than or equal to the channel's delay spread to each frame an operation limiting the maximum achievable data rate. As a remedy, this Letter advocates block transmissions in conjunction with orthogonal spreading sequences to remove the introduced IPI. The resultant scheme requires no channel knowledge besides timing offset and incurs slightly more complexity than non-block alternatives, while it increases the data rate at no cost in error performance. Given a fixed data rate of 25 Mbps, the novel block scheme exhibits about 1.8 dB gain relative to its non-block counterpart in single-user simulated tests.