nel is the same as that under flat 1 ICI Cancellation Techniques Based on Data Repetition for OFDM Systems Precoding Lowpass Modulation filtering Mirror Conversion/ mapping conjugate Decoding Discard Lowpass Demodulation filtering Conversion/ Mirror conjugate de-mapping Channel estimation Figure 1.7 Block diagram of an OFDM transceiver with the ICI two-path cancellation modules using mirror mapping in the baseband. fading channels, indicating that the CIR of the MCSR scheme is not affected by the channel length L. See Ref. [15] for proof. Accordingly, the average CIR of the MCSR scheme is given by (1.27) 1.4.2 Two-Path Cancellation with Mirror Mapping Figure 1.7 depicts the system architecture of the ICI two-path cancellation schemes with mirror mapping. The two-path cancellation schemes transmit data symbols in two consec- utive OFDM symbols, which are usually referred to as two independent paths separated by time division multiplexing (TDM). Evidently, the main additional operations due to the introduction of two-path cancellation schemes are integrated inside the precoding and decoding modules. In general, for the two-path cancellation schemes with mirror mapping, at the precod- ing module, one OFDM symbol input will become two OFDM symbol outputs (X(2),N-1, where the first OFDM symbol {X(superscript(1) N-1 k=0 is identical to the input OFDM symbol, i.e. and the second OFDM symbol {X(2) N-1 k=0 obeys the subcarrier mirror-mapping rule and can be obtained = {0, , N - 1}. For ease of exposition, if the conversion operation is utilized for the mapping operation, i.e. O(x) = -x, we refer to it as the MCVT scheme, and if the conjugate operation is used, i.e. O(x) = x*, we call it the MCJT scheme. After the deliberate design of the transmitted signal in the precoding module, the received signals at the m-th subcarrier and the (N - m)-th subcarrier of the first OFDM symbol and 1.4 ICI Cancellation Techniques the second OFDM symbol, respectively, will carry the same data information. Therefore, at the decoding module,