Circular-shift division multiple access with oversampling receivers

In this paper, a circular-shift division multiple access (CSDMA) scheme with oversampling receivers is proposed for multi-carrier multi-user wireless networks. The CSDMA scheme differentiates signals from different users by requiring each user to circularly shift their respective signals by a unique number of time domain samples. At the transmitter, each modulated data symbol is spread onto a subset of orthogonal subcarriers in the frequency domain, and the signals are then circularly shifted in the time domain. At the receiver, the received signals are oversampled in the time domain and then converted into the frequency domain for processing. The combination of circularly shifting at the transmitter and oversampling at the receiver ensures full multipath diversity, and it results in a special signal structure that allows the receiver to extract the signals from different users with zero or a small amount of multiple access interference (MAI). Both analytical and simulation results show that the proposed oversampled CSDMA scheme can achieve significant performance gains over conventional orthogonal frequency division multiple access (OFDMA) with the same spectral efficiency.