Inter-Carrier Interference Compensation for Zero Padding OFDM

Abstract

Zero Padded (ZP)-OFDM has attracted a lot of attention as an efficient technique to improve the performance in severe frequency selective channels, and many works were devoted to the equalization methods of ZP-OFDM in static channel models. In this paper, we propose the ICI compensation method corresponding to ZP-OFDM in the time and frequency selective channel. In the proposed method, the channel variation within one OFDM symbol is assumed to be linear to reduce the computational complexity. Simulation results show that the proposed method improves the performance in the frequency and time selective channels.

Time domain equalization method for TS-OFDM signal under higher mobile environments

“…From this fact, it is possible to employ the lowcomplexity parallel block inverse matrix algorithm [15] for solving (23). This feature of time domain CIR matrix for the proposed TDE method is completely different from the frequency domain CFR matrix for the conventional FDE methods of which CFR matrix is the full elements of matrix [3,[7][8][9][10][11][12]14]. Here it should be noted that although the CFR matrix of the conventional MMSE-FDE method for the CP-OFDM signal is not the banded matrix, it is possible to employ the parallel block inverse matrix algorithm by assuming that the elements in the CFR matrix both at the lower and upper sides of diagonal bands are small enough [10].…”

“…To solve the above problem, many frequency domain equalization methods were proposed to mitigate the ICI in higher time-varying channels [7][8][9][10][11][12][13][14]. These methods are designated as the frequency domain equalization (FDE) in which the equalization processing for the mitigation of ICI is conducted in the frequency domain.…”

“…However, the BER performance would be degraded in higher time-varying fading channels due to the approximation for the full elements of CFR matrix by the banded matrix. In [11], the fast sub-optimal FAST-MMSE-FDE method was proposed for the ZP-OFDM signal under the assumption of perfect channel knowledge. Although this method can achieve lower complexity by assuming the linear changing of CIR within one OFDM symbol period, it has a difficulty to estimate the CFR matrix precisely by using the pilot subcarriers in the frequency domain because the received pilot subcarriers are also affected by the ICI in higher time-varying fading channels [12].…”

“…These are completely different features from the conventional FDE methods of which CFR matrix is the full elements of matrix. The proposed TDE method can also obtain the frequency diversity gain at the fading deep dips [17] which enables to achieve better BER performance than the conventional FDE methods of using the CFR matrix as referred above [7][8][9][10][11][12][13][14].…”