Single-carrier fractional Fourier domain equalization system with zero padding for fast time-varying channels

Enqing Chen,Caihong Chu

doi:10.1186/1687-1499-2014-74

Abstract

Single-carrier frequency domain equalization (SC-FDE) has been shown to be an attractive transmission scheme for broadband wireless channels. However, its performance would degrade a lot if the channel is fast time-varying. In this paper, we analyzed the single-carrier fractional Fourier domain equalization (SC-FrFDE) system and applied it to the fast time-varying channel. It can solve the time-varying problem by selecting the optimal fractional Fourier transform order. To this SC-FrFDE system, its transmitter uses chirp-periodic circular prefix to eliminate ISI and this has an evident disadvantage that the receiver need to feedback the optimal fractional Fourier transform order to the transmitter through a feedback channel. To simplify the system, we propose to use zero padding (ZP) at the transmitter. There is already the overlap-add method as ZP in SC-FDE system. But the overlap-add method cannot be used in fast time-varying channels. Thus, we propose a new method as ZP. Simulation results show that our proposed method can significantly improve the system performance.

Highlights

Single-carrier frequency-domain equalization (SC-FDE) has been shown to be an attractive equalization scheme for broadband wireless channels which have very long impulse response memory [1]
6 Simulation results we present the simulation results of the zero padding (ZP)-SC-FrFDE, compared with chirp CP-SC-FrFDE and the conventional cyclic prefixed SC-FDE
We propose a new method to add ZP

Summary

Introduction

Single-carrier frequency-domain equalization (SC-FDE) has been shown to be an attractive equalization scheme for broadband wireless channels which have very long impulse response memory [1]. There needs a feedback channel between the transmitter and receiver to feedback the optimal fractional Fourier transform order. This will increase the complexity of the whole system. 2.1.2 Discrete time fractional Fourier transform (DTFrFT) The above is the FrFT of the continuous signal. To get the DFrFT of the time domain discrete signal, it is required to sample in the FrFD. According to the FrFT sampling theorem, the discretization of time domain and FrFD respectively cause chirp periodic extension of the FrFD and the time domain. This process is given as follows: Xpðm−N Þe−j12 cotαðm−NÞ2Δu2 1⁄4 XpðmÞe−j12 cotαm2Δu2. This chirp periodicity is very important because it will be used in the guard interval (GI)

Discrete fractional Fourier transform

N ÂN ðN þN c ÞÂN ð16Þ

Transmitter

Findings

Conclusions