Relaxed synchronization support of universal filtered multi-carrier including autonomous timing advance

Abstract

5G wireless systems may benefit by waveforms supporting relaxed synchronization, as this enables reduced energy consumption, better support of low-end devices and reduction of signaling overhead. In this paper we evaluate UFMC (Universal Filtered Multi-Carrier), also known as UF-OFDM (universal filtered OFDM) - the recently appeared waveform option for 5G - with respect to its performance in scenarios with relaxed synchronization. Both carrier frequency offset, e.g. due to low-cost oscillators used in low-end devices, and relative fractional delay, e.g. due to the absence of an energy consuming closed-loop ranging mechanism, is considered. We introduce a concept called autonomous timing advance (ATA) improving the overall system performance. With ATA the system can operate purely based on open-loop synchronization. For comparing UFMC with CP-OFDM, we evaluate the mean squared error (MSE) in the receiver after frequency conversion. With applying a limit regarding the tolerable amount of distortion, we calculate the supported link distance for a system applying either UFMC or CP-OFDM for LTE-like settings. With applying UFMC, higher link distances are supported than with CP-OFDM, if the system applies open-loop synchronization.