Performance evaluation of high mobility OFDM channel estimation techniques

Abstract

In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its robustness to multipath fading and high data rate transmissions. At the other hand, the performance of OFDM systems severely degraded due to multi-path fading and Doppler frequency shifts in mobile systems, which causes inter-carrier-interference (ICI). Thus, Estimation of channel parameters is required at the receiver using a pre designed estimator where pilot tones are inserted in each OFDM symbol. In this paper, a random pilot data are generated and inserted in each OFDM symbol at equally spaced locations. The performance test of Least Square (LS) and Linear Minimum Mean Square (LMMSE) estimation methods are proposed with Discrete Fourier Transform (DFT) based on both LS and LMMSE, where different ITU channel models are considered in order to compare their performance for data transmission in high mobile systems with different Doppler frequencies exceeds 200 Hz and minimal number of pilots.

Orthogonal frequency division multiplexing system with an indexed-pilot channel estimation

“…It is shown in [6] that the pilot patterns employed in OFDM systems for channel estimation determine the number of pilot symbols necessary to satisfy the targeted error performance. The minimum mean-squared error (MMSE) and the leastsquared (LS) techniques are widely used along with pilot-based channel estimation schemes [7]- [15]. For example, Sun and Wu [7] investigate pilot-insertion channel estimation with the MMSE estimator and identify the optimal-pilot percentage that results in the maximum spectral efficiency.…”

“…Compared to the LS estimator, the MMSE estimator has a high level of complexity [12]. However, in terms of performance, the MMSE estimator out performs the LS [13] [15]. An adaptive filter channel estimation scheme for multiinput-multi-output OFDM (MIMO-OFDM) systems is proposed in [16], where the authors show that the performance of MIMO-OFDM systems improves when coding and channel estimation are combined.…”

Performance evaluation of 4-quadrature amplitude modulation over orthogonal frequency division multiplexing system in different fading channels scenarios

“…Intercarrier interference (ICI) is eliminated when orthogonal subcarriers are used, and the signals carried on the various subcarriers do not interfere [6]. Hence, a simple frequency domain equalization method can be used [7]. IEEE 802.11 a, g, and n, IEEE 802.16a, and terrestrial digital video broadcasting (DVB-T) have all adapted it [8] and ODFM is used in digital subscriber line (DSL) and asymmetrical digital subscriber line (ADSL) for wired applications [9].…”

Field programmable gate array implementation of multiwavelet transform based orthogonal frequency division multiplexing system

“…Each one of these subcarriers is modulated by a data stream with low rate at different orthogonal carrier frequency [1]- [3]. In the traditional OFDM systems, the fast Fourier transform (FFT) is used for fulfilling the requirement of orthogonality between the different subcarriers [4]- [8]. FFT has a major drawback arising from using rectangular window, which creates high side lobes in the transmitting signals, thereby increase sensitivity of the OFDM system to the Inter-Carrier Interference (ICI) and a low system performance [9]- [14].…”