Robust timing synchronization for uplink multi-carrier spread-spectrum systems

A combination of multi-carrier modulation (e.g., OFDM) and spread-spectrum (e.g., DS-CDMA) called MC-SS is considered as a potential candidate for the wireless 4G technology. Most present synchronization techniques for OFDM can also be used for the downlink MC-SS system. However, they are not suitable for the uplink MC-SS system because every user´s signal arrives at the base station asynchronously. In this paper, we propose a patterned timing synchronization algorithm which can estimate the signal arrival times for every user. Simulation results show that the performance of the proposed timing synchronization algorithms are close to ideal in the presence of multipath fading channels with frequency offsets up to several carrier spacings