g to some carefully designed subcar- rier mapping rules and operations such that after combining the mirror subcarrier pairs carrying the same information, the CIR can be significantly improved. The MSR and MCSR schemes repeat the data within one OFDM symbol, while the MCVT and MCJT schemes repeat the data across two consecutive OFDM symbols. All these four ICI cancellation schemes feature the simplicity of implementation and the effectiveness of ICI mitigation. 1.4.1 One-Path Cancellation with Mirror Mapping Figure 1.6 depicts the system architecture of the ICI one-path cancellation schemes with mirror mapping. Compared with the plain OFDM, the ICI one-path cancellation schemes have two additional modules, i.e. the ICI self-canceling modulation before the IFFT opera- tion at the transmitter and the ICI self-canceling demodulation after the FFT operation at the receiver. For the ICI self-canceling modulation, the input modulated data symbols are first grouped into transmit blocks. Each block consists of (N/2 - 1) modulated data symbols N/2-1 , which are then mapped onto N subcarriers using the one-to-two mirror-mapping rule as follows: k=0,N/2 k=1,2,...,N/2 - 1 (1.21) N_k),k=N/2+1,...,N- - 1, where are the actual transmitted data symbols on the OFDM subcarriers. O(x) is defined as the mapping operation that reflects the relationship between the two modulated data symbols with the same information. Note that (),k=1, = 2, N/2 - 1 rep- resents mirror mapping. 1 ICI Cancellation Techniques Based on Data Repetition for OFDM Systems ICI self-canceling modulation Mirror Conversion/ Modulation Lowpass Add CP mapping conjugate filtering ICI self-canceling demodulation Conversion/ Mirror Discard Demodulation Lowpass conjugate de-mapping filtering Channel estimation Figure 1.6 Block diagram of an OFDM transceiver with the ICI self-cancellation modules using mirror mapping in the baseband. After the ICI self-canceling demodulation, the received signals on subcarrier m, m E 2, ... , N/2 - 1} and its corresponding mapped subca