Iterative Successive Interference Cancellation Scheme To Remove Multi User Interference Due To Carrier Frequency Offsets In Ofdma Uplink

Iterative Successive Interference Cancellation Scheme to Remove Multi User Interference Due to Carrier Frequency Offsets in OFDMA Uplink

Orthogonal Frequency Division Multiple Access (OFDMA) is similar to OFDM but has its subcarriers allocated to different users using different Carrier Allocation Schemes. In OFDMA, the fact that each user has a different Carrier Frequency Offset (CFO) makes the Interference Cancellation more challenging than OFDM systems. CFO can destroy orthogonality among subcarriers. This results in Inter-Carrier Interference (ICI), i.e., Interference among subcarriers of the same user, and Multi-User Interference (MUI), i.e., Interference due to other users. It induces significant performance degradation. Eliminating MUI is more challenging at the base station of an OFDMA system because of multiple CFOs. In this paper, we present an improvement to a Successive Interference Cancellation (SIC) scheme to compensate CFO by removing MUI on users. In the SIC scheme, a decorrelator is used to remove the ICI within a user's signal and successive cancellation is applied to mitigate the MUI arising due to the frequency difference among uplink users. We extend this scheme by following the SIC scheme first and then doing a re-iteration successively in the reverse order to eliminate MUI of each user on every other user. The proposed improvement is investigated for performance.

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Interference Cancellation Scheme for Carrier Frequency Offsets Compensation in the Uplink of OFDMA Systems