Pulse shaping for direct-sequence offset quadrature-spread UWB communication signals

The paper addresses the performance analysis of pulse-shaped direct-sequence ultra-wideband (UWB) communication systems employing offset quadrature phase shift keying (OQPSK). The proposed system offers many advantages over carrier-less UWB schemes, as pulse-shaped OQPSK spreading gives better phase randomization in multi-user interference scenarios, and is also useful for minimizing large phase jumps in the modulated signals, which reduces spectral re-growth and adjacent channel interference, particularly in the presence of non-linear amplifiers. Bit error probability results are derived for fading channels with selection diversity and maximum ratio combining receivers. Numerical examples with pulse shapes based on Gaussian monocycle derivatives and modified Hermite polynomials are given to illustrate the relative performance comparisons among different chip pulse shapes and diversity combining techniques.