 has exactly the same expression as that in AWGN channels. 1.4.3 CIR Comparison An OFDM system with N = 1024 subcarriers is considered for comparing the CIR perfor- mance among plain OFDM, adjacent-mapping-based schemes, and mirror-mapping-based schemes. Figure 1.8 presents the CIR results of flat fading channels, i.e. L = 1. For the ICI two-path cancellation schemes, CIR results with AE = 0 and AE = 0.03 are presented. From Figure 1.8, the following facts can be observed: All mirror-mapping-based schemes express much better CIR performance than plain OFDM. MSR and MCSR outperform ASR and ACSR, respectively. This shows that the mirror-mapping rule has better ICI suppression capability than the adjacent-mapping rule. The main reason is that for the mirror-mapping-based schemes, the interference from neighbor subcarriers is sufficiently suppressed, while there is still some residual interference from neighbor subcarriers for the adjacent-mapping-based schemes. With AE = 0, the CIR curves of the MCSR scheme and the MCJT scheme coincide, and the CIR of the MSR scheme is close to that of the MCVT scheme. This is because the same operation is adopted for both schemes. With AE = 0, the CIR performance of the conversion-based schemes, namely MSR and MCVT, is better than that of the conjugate-based schemes, namely MCSR and MCJT. 1.5 Experiment on Sea Normal OFDM MCVT, A& = 0 MCJT, AE = 0 MCVT, AE = 0.03 MCJT, AE = 0.03 Figure 1.8 CIR comparison among the plain OFDM, adjacent-mapping-based schemes, and mirror-mapping-based schemes for different values of E over flat fading channels. This is because in their CIR expressions Sk+Stk 22 0 is a rougher approximation than Sk + S_k 22 0. With AE = 0.03, the CIR performance of the MCVT scheme and the MCJT scheme is degraded due to the CFO deviation between the first OFDM symbol and the second OFDM symbol. Figures 1.9 and 1.10 present the CIR results of multipath Rayleigh fading channels. Assume that each channel tap has the same power, i.e. of =02=...= -. The effect of the channel