Modified Correlative Coding for Frequency Offset Mitigation in OFDM Systems

The focus of this paper is on the correlative coding used to mitigate frequency offset in orthogonal frequency division multiplexing (OFDM) systems in mobile radio applications, such as 802.11a, 802.16, and digital video broadcasting (DVB) systems, e.g., DVB-CS2. This frequency offset may result due to the time variations of the channel during one OFDM symbol interval, or the transmitter and receiver are not phase locked, which in turn destroys orthogonality between different subcarriers, leading to power leakage among the subcarriers, known as Inter-Carrier Interference (ICI). A carrier - to - interference ratio (CIR) will be derived for the (1 - D - D2) correlative codes and the modified scheme. A comparison between the different correlative coding orders will be held considering the CIR and bit error probability for each scheme at different normalized frequency offset values.