We propose a novel detection method for non-coherent synchronization (signal acquisition) in multi-user UWB impulse radio (IR) networks. It is designed to solve the IUI (Inter-User Interference) that occurs in some ad-hoc networks where concurrent transmissions are allowed with heterogeneous power levels. In such scenarios, the conventional detection method, which is based on correlating the received IR signal with a Template Pulse Train (TPT), does not always perform well. The complexity of our proposal is similar to that of the conventional method. We evaluate its performance with the Line Of Sight (LOS) and the Non LOS (NLOS) office indoor channel models proposed by the IEEE P802.15.4a study group and find that the improvement is significant. We also investigate the particular case where the concurrent transmissions have the same time-hopping code, and we show that it does not result in collision, such scenarios appear in ad-hoc networks that employ common code for control or broadcast purposes.