Cancellation of Multiuser Interference due to Carrier Frequency Offsets in Uplink OFDMA

In uplink orthogonal frequency division multiple access (OFDMA) systems, multiuser interference (MUI) occurs due to different carrier frequency offsets (CFO) of different users at the receiver. In this paper, we present a multistage linear parallel interference cancellation (LPIC) approach to mitigate the effect of this MUI in uplink OFDMA. The proposed scheme first performs CFO compensation (in time domain) followed by K DFT operations (where K is the number of users) and multi-stage LPIC on these DFT outputs. We present a detailed performance and complexity comparison of the proposed scheme with another scheme proposed recently by Huang and Letaief which performs CFO compensation and interference cancellation in frequency domain using Circular Convolution (we refer to this scheme as HLCC scheme). We show that the HLCC scheme performs better than our scheme when the individual CFO values are small, whereas our scheme performs better than the HLCC scheme when the CFO differences are small (even if the individual CFO values are large). Also, our scheme has lesser complexity than HLCC scheme when the number of subcarriers is large, which is typical in OFDMA systems.