Timing synchronization is a critical as well a challenging issue in ultra-wideband impulse radio (UWB-IR) due to their particular transmission characteristics. This letter proposes a rapid synchronization algorithm which can achieve frame-level synchronization in non-data-aided (NDA) mode. Relying on a unique transmit signal pattern based on orthogonal pulses and asymmetric modulation, synchronization is achieved without the need to search among thousands of bins, thereby significantly reducing the mean synchronization time. Simulation results prove that the proposed synchronization algorithm is efficient in single as well as in multi-user scenarios.