Residual Frequency Offset Compensation-Embedded Turbo Decoder

We propose a modified turbo decoder that internally includes the residual frequency offset compensation function in an iterative decoding process. Based on the recently proposed phase offset compensation scheme that embeds phase compensation into iterative turbo decoding, we extend it to cover frequency offset compensation. At each decoding iteration, we estimate the residual frequency offset from the extrinsic information and compensate it for the next iteration. As the iteration goes on, the frequency offset is gradually and drastically reduced. Consequently, the severe turbo decoding failure due to even a small residual frequency offset can be significantly recovered, and then, almost ideal decoding performance is achieved. In particular, for power-limited communications under a very-low-SNR environment where even a tiny frequency offset is critical to turbo decoding, the proposed scheme is efficient since it does not require additional transmission power for compensation.